We use a phrase about how something is all-inclusive that is similar to this. When talking about the animals from A to Z or how you can get anything from A to Z from Amazon.com. What we are saying is that this is all of it, everything. That is what Jesus is saying about himself here. There is a song I remember singing, “He Is My Everything”, that expressed this idea and encouraged us to help others see their need for Jesus to be their all as well.
Just as God is described as the One who gives us all things and in whom we live and move and have our being (Acts 17:25-28), Jesus is described in Colossians 1:16-17 as having all things created by and for him and being the one who holds all things together. Whatever you need from A to Z, Jesus is the one who can provide it. Have you made Jesus your everything. Like the youth song says do you believe and live the words: “You are my strength when I am weak, You are the treasure that I seek, You are my all in all. Seeking You as a precious jewel, Lord to give up I’d be a fool. You are my all in all.”