The Apostles' Creed, though not written by the apostles, is the oldest creed of the Christian church and is the basis for others that followed. Its most used form is:
I believe in God the Father Almighty, Maker of heaven and earth, And in Jesus Christ his only Son our Lord, Who was conceived by the Holy Ghost, Born of the Virgin Mary, Suffered under Pontius Pilate, Was crucified, dead, and buried. He descended into hell; The third day He rose again from the dead; He ascended into heaven, And sitteth on the right hand of God the Father Almighty; From thence he shall come to judge the quick and the dead. I believe in the Holy Ghost; The Holy catholic Church, the Communion of Saints; The Forgiveness of sins; The Resurrection of the body, And the Life everlasting. Amen.
In its oldest form, the Apostles' Creed goes back to at least 140 A.D. Many of the early church leaders summed up their beliefs as they had an opportunity to stand for their faith see, for example, 1 Timothy 6:12. These statements developed into a more standard form to express one's confession of faith at the time of baptism. It is not Scripture, but it is a simple list of the great doctrines of the faith.
The word "catholic" means "relating to the church universal" and was the word used in the original version of the Creed. It does not mean the Roman Catholic Church, but the church, the body of Christ, as a universal fellowship. The phrase, "He descended into hell," was not part of the creed in its earliest form.