Christ (The Word) was created into Eternity therefore he is also Eternal but His Father has always been Eternal.
Eternity by definition is indefinite and unending. It has no beginning and no end.
Psalms 90:2 reveals God has existed forever.
Psalms 93:2 reveals God is from time indefinite. Job 36:26 says God is beyond our comprehension. His eternal existence cannot be measured by our inferior minds. Our limited thinking and reasoning process cannot comprehend eternity.
We are instilled with a beginning for our start in creation. We cannot fathom anything in existence that did not have a beginning.
When did the "Beginning" come into existence? John: 8-58, Jesus revealed that he (Jesus the Word) existed even before Abraham came into existence. Abraham was born well before Jesus made his human appearance on this planet. Jesus was imparting a revelation, in that he had existed with his Father at an earlier time in eternity.
How do we know that Jesus existed during eternity with his Father? John 17:5 answers that question. He has glory along side
his Father prior to the creation of the world. So, was that the "Beginning?" It was a beginning, but not our beginning. It was still etrnity
at that time.
Revelation 1:1 and Revelation 3:14 reveals that Jesus was the beginning of the first creation by his Father.
Colossians 1:15 reveals Jesus was made in the image of his Father.
We also know that he existed with his Father before coming to Earth because of what is revealed at John 6:62.