The First Council of Nicaea (Modern Turkey) in 325 created the Nicene Creed as part of the profession of faith required of those undertaking important functions within the Catholic Church.
The purpose of a creed is to provide a doctrinal statement of correct belief or orthodoxy. The Nicene Creed was created as a result of the extensive adoption of the doctrine of Arius far outside Alexandria, in order to clarify the key tenets of the Christian faith.
The Nicene Creed of 325 explicitly affirms the co-essential divinity of Jesus as the Son of God. The 381 version speaks of the Holy Spirit as worshipped and glorified with the Father and the Son.
The Creed is the basis of the profession of faith within Christianity, it was originally written as follows..
We believe in one God, the Father Almighty, maker of all things visible and invisible.
And in one Lord Jesus Christ, the Son of God, begotten of the Father, the only-begotten; that is, of the essence of the Father, God of God, Light of Light, very God of very God, begotten, not made, being of one substance with the Father.
By whom all things were made both in heaven and on earth; who for us men and for our salvation, came down and was incarnate and was made man; He suffered, and the third day he rose again, ascended into heaven; From thence he shall come to judge the quick and the dead. And in the Holy Ghost.