A creed is a summary of Christian beliefs that are held by a group of churches. Creeds are used for at least three purposes: 1) as part of a statement of faith regarding what a church believes, and 2) to instruct, and 3) to distinguish what a particular group of believers believe from an opposing position.
The Apostle’s creed is an early statement of Christian belief. It is Trinitarian in structure.
The Nicene Creed is a statement of orthodox Christian belief in opposition to certain heresies, especially Arianism.
The Chalcedonian Definition (or Chalcedonian Creed) states that Jesus is one person with two natures.
The Athanasian Creed focuses on the Trinity and on Christology.