A creed (also known as a confession, symbol, or statement of faith) is a statement of the shared beliefs of a religious community in the form of a fixed formula summarizing core tenets.
One of the most widely used creeds in Christianity is the Nicene Creed, first formulated in AD 325 at the First Council of Nicaea. It was based on Christian understanding of the Canonical Gospels, the letters of the New Testament and to a lesser extent the Old Testament. Affirmation of this creed, which describes the Trinity, is generally taken as a fundamental test of orthodoxy for most Christian denominations. The Apostles' Creed is also broadly accepted. Some Christian denominations and other groups have rejected the authority of those creeds.
–Wikipedia