Perfect, Absolute Existence

God said to Moses, “I am who I am. " And he said, “Say this to the people of Israel, ‘I am has sent me to you.’” ( Exodus 3:14)

"AM" - hayah (hawyaw) in Hebrew. Means Exist. To Be.
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Jesus said to them, “Truly, truly, I say to you, before Abraham was, I am.” (John 8:58)

"AM" - Eime (ieemee) in Greek. Is, Am, Was, Have Been. Exist.

The best interpretation I've ever heard for this phrase is
"Perfect, absolute existence."

He is the source of all that is.

“I am the Alpha and the Omega,” says the Lord God, “who is and who was and who is to come, the Almighty.” Revelation 1:8

I am the Alpha and the Omega, the first and the last, the beginning and the end.” Revelation 22:13

For by Him all things were created, both in the heavens and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things have been created through Him and for Him. He is before all things, and in Him all things hold together. Colossians 1:16-17

Jesus Christ is God. He did all the work in creation. Nothing exists that He did not create, by and for Himself. He not only created, but He also sustains all that exists. What we see, what we don't see. God the Father planned it. God the Spirit reveals it. God the Son produced---everything! Of course we cannot comprehend the magnitude of His power, but We are His, brethren, and He is ours! Hallelujah!