This is based on Encyclopaedia Britannica articles. For more detail, please find Encyclopaedia Britanica on the web at www.eb.com. Very many thanks to Anthony Murphy for ediiting various sections.
Founded in the 1st century AD by Jesus of Nazareth (the Christ, or the Anointed One of God), Christianity has become the largest of the world's religions
Its largest groups are the Roman Catholic Church, the Eastern Orthodox churches, and the Protestant churches; in addition to these churches there are several independent churches of Eastern Christianity as well as numerous sects throughout the world.
The 20th century has seen an explosion of publicly available information concerning the wider religious life of humanity, as a result of which the older Western assumption of the manifest superiority of Christianity has lost plausibility in many minds. Christians today adopt one of three main points of view. One is exclusivism, which holds that there is salvation only for Christians. The exclusivist outlook was eroded within advanced Roman Catholic thinking in the decades leading up to the second Vatican Council (1962-65) and was finally abandoned in the council's pronouncements. Within Protestant Christianity there is no comparable central authority, but most Protestant theologians, except within the extreme Fundamentalist constituencies, have also moved away from the exclusivist position. Inclusivism is the second view that, although salvation is by definition Christian salvation, brought about by the atoning work of Christ, it is nevertheless in principle available to all human beings, whether Christian or not. The third position, to which a number of individual theologians have moved in recent years, is pluralism. According to this view, the great world faiths, including Christianity, are valid spheres of a salvation that takes characteristically different forms within each--though consisting in each case in the transformation of human existence from self-centredness to a new orientation toward the Divine Reality. The other religions are thus not secondary contexts of Christian redemption but independently authentic paths of salvation. The pluralist position is controversial in Christian theology because it affects the ways in which the doctrines of the person of Christ, atonement, and the Trinity are formulated.