"I tell you the truth, it is not Moses who has given you the bread from heaven, but it is my Father who gives you the true bread from heaven. For the bread of God is he who comes down from heaven and gives life to the world." (John 6:32)

Here Jesus is responding to this question being asked:
"What miraculous sign then will you give that we may see it and believe you? What will you do? Our forefathers ate the manna in the desert; as it is written: 'He gave them bread from heaven to eat.'" (John 6:30)
In answering them, Jesus is clarifying that it is the Supreme Being who is conducting miracles and dispatching His representatives. It is the Supreme Being who is sending His loving servants like Moses, Solomon, David, Abraham, Jonah, Job, John the Baptist and Jesus. It is the Supreme Being who is empowering them to teach His message and perform miracles.

Those questioning Jesus were talking about the Exodus, when Moses led the Israelites out of slavery and to Canaan. Please see below for an alternative translation* of this verse.

What is the "true bread from heaven?" 

The "true bread from heaven" is the opportunity to re-connect with God, and re-develop ones loving relationship with God.

Ultimately, only the Supreme Being can give us this opportunity, but He may utilize one of His loving servants to communicate through. Through His representatives, the Supreme Being can also illustrate to us how we can make changes in our lives in order to advance in our own relationship with God. 

This is because God's representatives already have a loving service relationship with God, and they can show us how we can also achieve that. This is the meaning of "For the bread of God is he who comes down from heaven and gives life to the world."

The loving servant and representative of God enjoys a transcendental relationship with the Supreme Being. While we cannot see that relationship with the physical eyes, we can know of it by seeing the activities of the loving servant of God. Seeing those activities - seeing the loving servant of God sacrifice his entire life to the Supreme Being - is the means by which we can see the extent of their relationship. In the case of Jesus, we can see the extent of his relationship with the Supreme Being by Jesus' life.

In other words, Jesus didn't just teach with words. He also taught with his actions. Through his life we can see what a devoted loving servant does to please God.

And what did Jesus do to please his beloved Master and Father, the Supreme Being

He gave up everything. Just think about it. Jesus walked from town to town with no possessions, no home, and even though many criticized him, he never waivered in his teachings and his mission to serve the Supreme Being.

Then Jesus gave the ultimate sacrifice in the physical: His physical body. Because he would not budge or retract any of his teachings, Jesus was persecuted, tortured and murdered. Jesus could have escaped such a fate if he wanted to. But instead, he carried on in his mission to please the Supreme Being.

This is the "stuff" of love. This is the "stuff" of devotion, and the reason why "he who comes down from heaven and gives life to the world" is the "bread of God"  is because the lives and teachings of God's representative reveals the intense loving relationships that exist between the Supreme Being and His devoted children - who dwell in the spiritual world with Him.

*Here is the translation of this verse according to the Gospels of Jesus:

“Very truly I say to you, it is not Moses who has given you the food from heaven, but it is my LORD who gives you the true food from the spiritual realm.” (John 6:32)