This literally means to attain enlightenment and reunite with Him.
"Me and my father are one"
Jesus was enlightened and as such he realized himself as God.
I am God, you are God; it is just the mind which covers this fact. But it is absurd; how can the finite mind cover the infinite? It is like expecting a molecule of water to cover the ocean; it is clearly impossible.
You see God is God with no differentiating factors. Even if God did desire to create us he would still be us. The separation between God and us would be God and we as well would be God. This makes the apparent creation of us God. There was never a change and nothing was created; how can God be anything but God?
A drop of water in water is still water. God in God is still God.