"In the beginning was the Word"—this is the opening declaration of John (1:1). The Word of God, the first crystal in the Gospel of John, refers to Christ, the only begotten Son of God (v. 18), as the definition, explanation, and expression of God.
John unveils Christ as the great "I Am," self-existing and ever-existing (Exo. 3:14-15; John 8:24, 28, 58). Everything other than Christ is vanity of vanities. Only He is the reality, the I Am, the One who is.
Christ is the One who is eternal, without beginning or ending (Heb. 7:3).
John 1 is the introduction to the whole Gospel of John, and the main stress of this introduction is that Christ is the Word of God—the definition, explanation, and expression of the mysterious and invisible God. It refers to Christ in the five greatest events in the history of the universe.
John 1 reveals Christ in the creation of all things in the beginning of time (v. 3).