The claim at the centre is historical rather than philosophical: that a particular man, in a particular decade, under a named Roman governor, was executed and then raised. Almost everything else follows from what Christians make of that.
From it comes the doctrine of the incarnation, that Jesus is not a messenger about God but God present as a human being, and the Trinity, the insistence that Father, Son and Spirit are one God rather than three, which took the church four centuries and several councils to state in words most of it could accept. The Nicene Creed of 325, revised in 381, is still recited by Catholics, Orthodox and most Protestants alike, and remains the nearest thing to a shared text.
Salvation is understood as something done for humanity rather than achieved by it, though the traditions differ sharply on what is required in response: the Reformation turned on precisely that question. Scripture is the Old and New Testaments, though the canon is not identical across traditions, Catholic and Orthodox Bibles include books Protestants set aside at the Reformation.
Two rites are near-universal. Baptism marks entry; the Eucharist re-enacts the last meal Jesus ate before his death. What that meal is, a real presence, a memorial, something between, is one of the oldest and least resolved disagreements in the religion.