The word "creed" comes from the Latin credo, which means, "I believe." It is a concise statement of faith or beliefs held by a religious institution, outlining and clarifying that which sets the institution apart from others.
The Apostles' Creed, the Nicene Creed, and the Westminster Confession are just three examples of the many creeds developed to define the Christian Church or an individual tradition within it.
There are many Christian traditions, Baptists and Quakers being only two, that do not promote the use of creeds. But the majority of Christian denominations, being so influenced by Greek, systematic thought, use creedal formulas, which new members are expected to affirm when being baptized or confirmed.