In about AD 107, Saint Ignatius, Bishop of Antioch wrote to Christians in Smyrna. His letter is the earliest surviving witness to the use of the term "catholic Church." (Smyrnaeans, 8). By it Saint Ignatius designated the Christian Church in its universal aspect, excluding heretics, such as those who "confess not the Eucharist to be the flesh of our Saviour Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again." (Smyrnaeans, 7). He called such people "beasts in the shape of men, whom you must not only not receive, but, if it be possible, not even meet with" (Smyrnaeans, 4).

Yet more explicit was the manner in which Saint Cyril of Jerusalem (circa 315-386) used the term "catholic Church" precisely to distinguish this Church from heretical "Churches". He urged: "If ever thou art sojourning in cities, inquire not simply where the Lord's House is (for the other sects of the profane also attempt to call their own dens houses of the Lord), nor merely where the Church is, but where is the Catholic Church. For this is the peculiar name of this Holy Church, the mother of us all, which is the spouse of our Lord Jesus Christ, the Only-begotten Son of God" (Catechetical Lectures, XVIII, 26).[1]

The word Catholic has been used ever since to describe the genuine one original Church founded by Christ and the Apostles. The word appears in the main Christian creeds (formal definitions of belief), notably the Apostles' Creed and the Nicene Creed. As such, many Christians claim entitlement to the designation "catholic". These fall into two groups:

Christians of most denominations, including most Protestants, affirm their faith in "One Holy Catholic and Apostolic Church". For Protestants, most of whom consider themselves to be spiritual descendants (category 2, above), this affirmation refers to their belief in the ultimate unity of all churches under one God and one Saviour, rather than in one visibly unified institutional church (category 1, above). In this usage catholic is sometimes written with a lower-case "c". The Western Apostles Creed, stating "I believe in...the holy catholic church..." (sometimes capitalised), is thus recited in Protestant worship services (with the notable exception of German Lutherans). The Nicene Creed likewise declares belief in "one holy catholic and apostolic Church".

The early Catholic Church came to be organized under the three patriarchs of Rome, Alexandria and Antioch, to which later were added the patriarch of Constantinople and of Jerusalem. The Bishop of Rome was at that time recognized as first among them, and doctrinal or procedural disputes were sometimes referred to Rome. When the Imperial capital moved to Constantinople, Rome's influence was often challenged. While Rome claimed special authority and descent from St. Peter and Saint Paul, who, all agreed, were martyred and buried in Rome, Constantinople had become the residence of the Emperor, and the churches at Antioch, and Alexandria were all older than Rome. Antioch furthermore was considered to have been the see of St. Peter before he went to Rome.

The AD 431 Council of Ephesus, the Third Ecumenical Council, was chiefly concerned with Nestorianism. Nestorianism emphasized the distinction between the humanity and divinity of Jesus and taught that the Virgin Mary gave birth not to God but only to the man, Jesus Christ. This Council rejected Nestorianism and affirmed that humanity and divinity were inseparable in the one person Jesus Christ, and that his mother, the Virgin Mary, is thus 'Theotokos,' God-bearer, Mother of God. The first great rupture in the Church followed this Council)\. Those who refused to accept the Council's ruling were largely Persian and are represented today by the Assyrian Church of the East and related Churches..

The next major break was after the Council of Chalcedon (AD 451). This Council repudiated Eutychian Monophysitism which states that the divine nature completely subsumed the human nature in Christ. This Council declared that Christ, though one person, exhibited two natures "without confusion, without change, without division, without separation" and thus is both fully God and fully human. The Alexandrian Church rejected the terms adopted by this Council. These Christians are now often referred to as Ancient Oriental Churches or the Oriental Orthodox Communion.

The next major rift within Christianity was in the 11th century. Doctrinal disputes, as well as conflicts between methods of Church government, and the evolution of separate rites and practices, precipitated a split in AD 1054 that divided the Church, this time between a "West" and an "East". England, France, the Holy Roman Empire, Scandinavia, and much of the rest of Western Europe were in the Western camp, and Greece, Russia and many of other Slavic lands, Anatolia, and the Christians in Syria and Egypt who accepted the Council of Chalcedon made up the Eastern camp. This division is called the Great Schism. The most recent major division in the Church occurred in the 16th century with the Protestant Reformation, after which many parts of the Western Church rejected the teachings of the Roman Catholic Church and became known as "Protestant".

The largest by far of all groups that call themselves Catholic is the Roman Catholic Church, which its members normally call simply the Catholic Church, a usage - like that by which the term “Catholic” is often employed as synonymous with “Roman Catholic” - that others describe as contentious. The adjective "Roman" is used of this Church in reference to the centrality for it of the Bishop of Rome, with whom Roman Catholics are by definition in full communion, as part either of the majority Latin (Western) particular Church or of her 20 smaller Eastern Rites.

In Western Christianity the principal groups that regard themselves as "Catholic" without full communion with the Pope are the Chinese Patriotic Catholic Association and some elements of Anglicanism ("High Church Anglicans" or "Anglo-Catholics"). Smaller groups include the Old Catholics, the Aglipayans (Philippine Independent Church), and the Polish National Church of America. Their spiritual beliefs and practices are similar to those of Catholics of the Latin Rite, from which they emerged, but they reject the Pope's claimed status and authority.

The Anglican Communion is in practice divided into two wings, "High Church Anglicans" also called the Anglo-Catholics and "Low Church Anglicans" also known as the Evangelical wing. Though all elements within the Anglican Communion recite the same creeds, Low Church Anglicans regard the word Catholic in the ideal sense given above, while High Church Anglicans treat it as a name of Christ's church which they consider to embrace themselves together with the Roman Catholic and several Orthodox Churches.

Anglo-Catholicism maintains similarities to the Latin Rite of Roman Catholicism and related spirituality, including a belief in seven sacraments, Transubstantiation as opposed to Consubstantiation, devotion to the Virgin Mary and saints, the description of their ordained clergy as "priests" — addressed as "Father" — the wearing of vestments in church liturgy, sometimes even the description of their Eucharistic celebrations as "Mass". The development of the Anglo-Catholic wing of Anglicanism occurred largely in the nineteenth century and is strongly associated with the Oxford Movement. Two of its leading lights, John Henry Newman and Henry Edward Manning, both ordained Anglican clergymen, ended up joining the Roman Catholic Church, becoming cardinals.

The several churches of Eastern Orthodoxy and Oriental Orthodoxy each consider themselves to be the universal and true Catholic Church, and typically regard the other of these families and the Western Catholics as heretical and as having left the One Holy Catholic, and Apostolic Church. The patriarchs of these Eastern Orthodox and Oriental Orthodox Churches are autocephalous hierarchs, which roughly means that each of them is independent of the direct oversight of another bishop (although still subject, according to their distinct traditions, either to the synod of bishops of each one’s jurisdiction, or only to a common decision of the patriarchs of their own communion). They are willing to concede a primacy of honor to the Petrine See, but not of authority.

Their belief that the Church is the vessel and deposit of the fullness of the teachings of Jesus and the Apostles from which the Scriptures were formed. This teaching is preserved in both written Scripture and in written and oral church Tradition. Neither is independent of the other.

Belief that the Eucharist is really, truly, and substantially the Body and Blood of Christ, which occurs through transubstantiation. Those that are quite distinctively Catholic believe that adoration and worship is due to the Eucharist as the body and blood of Christ.

A distinction among worship (latria) for God, and veneration (dulia) for saints, with the term hyperdulia used for a special veneration accorded to the Virgin Mary among the saints. Some do not accept the distinction between hyperdulia and dulia.

Baptism is the first and basic sacrament of Christian initiation. Catholics consider baptism conferred in most Christian denominations "in the name of the Father and of the Son and of the Holy Spirit" (cf. Matthew 28:19) to be valid, since the effect is produced through the sacrament, independently of the faith of the minister, though not of the minister's intention.

Confirmation or Chrismation is the second sacrament of Christian initiation. It is conferred by the laying on of hands and anointing, together with a special consecratory prayer. Through it, the gift of the Holy Spirit conferred in baptism is "strengthened and deepened" (see Catechism of the Catholic Church §1303). Its "originating" minister is a validly consecrated bishop; if a priest (a "presbyter") confers the sacrament - as is done ordinarily in Eastern Churches and in particular cases in Western - the link with the higher order is indicated by the use of myrrh blessed by a bishop (in an Eastern Orthodox Church, by the patriarch]]). In the East the sacrament is administered immediately after baptism. In the West administration came to be postponed until the recipient’s early adulthood; but in view of the earlier age at which children are now admitted to reception of the Eucharist, it is more and more restored to the traditional order and administered before giving the third sacrament of Christian initiation.

The Eucharist is the sacrament (the third of Christian initiation) by which Catholics partake of the Body and Blood of Jesus Christ and participate in his one sacrifice. The bread and wine used in the rite are, in Catholic faith, considered to be transformed in all but appearance into the Body and Blood of Christ, a change that is commonly called transubstantiation.

Penance and Reconciliation are names given to the first of two sacraments of healing, which is also called the sacrament of conversion, of confession, and of forgiveness (Catechism of the Catholic Church, 1423-1424).[2] It is the sacrament of spiritual healing of a baptized person from the distancing from God involved in sins committed. It involves four elements: the penitent's contrition for sin (without which the rite does not have its effect), confession to a priest (it may be spiritually helpful to confess to another, but only a priest has the power to administer the sacrament), absolution by the priest, and satisfaction. In early Christian centuries, the fourth element was quite onerous and generally preceded absolution, but now it usually involves a simple task (in some traditions called a “penance”) for the penitent to perform, to make some reparation and as a medicinal means of strengthening against further temptation.

Anointing of the Sick is the second sacrament of healing. In it those who are suffering a serious physical illness are anointed by a priest with oil blessed specifically for that purpose. "Seriously sick" does not necessarily mean "in immediate danger of death". In past centuries, when such a restrictive interpretation was customary, the sacrament came to be known as "Extreme Unction", i.e. "Final Anointing". It was then conferred only as one of the "Last Rites". The other "Last Rites" are Confession (if the dying person is physically unable to confess, at least absolution, conditional on the existence of contrition, is given), and the Eucharist, which when administered to the dying is known as "Viaticum", a word whose original meaning in Latin was "provision for a journey".

Holy Orders is the sacrament by which one becomes a bishop, a priest or a deacon. Only a bishop may administer this sacrament. Ordination as a bishop confers the fulness of the sacrament, making the bishop a member of the body that has succeeded to that of the Apostles, and giving him the mission to teach, sanctify and guide, along with the care of all the Churches. Ordination as a priest configures the priest to Christ the Head of the Church and the one essential Priest, empowering him, as the bishops' assistant, to celebrate divine worship, especially the Eucharist. Ordination as a deacon configures the deacon to Christ the Servant of All, placing him at the service of the Church, especially in the fields of the ministry of the word, divine worship, pastoral guidance and charity.