In the 3rd century A.D. the Christian church was exploding in size around the Roman Empire. Most of the population of the empire however was made up of people with little to no formal education, who could not read and write. This meant that most of the church members could not study or read the scriptures to know the beliefs of their religion. Church leaders were worried that members could be misled so they had to come up with a way to teach the same beliefs to all people... enter the Creed.
The earliest version of a Christian statement of beliefs was the Apostles' Creed, which first appeared about 215 AD.
It is a simple statement, short enough for anyone to memorize and understand.
The Apostles' Creed has been in use for 1800 years. Here is a modernized version.
In 325 A.D church leaders got together for the Council of Nicea to discuss the beliefs or doctrine of the Christian Church.
From this conference they created the Nicene Creed; a poem type statement that includes all the most fundamental parts of Christianity.
This Creed could then be memorized by all Christians, giving them a way to be secure in their beliefs.