What does John 6:49 mean?

When Jesus initially claimed that He is the Bread of Life, and that eternal life was offered only to those who believe in Him, the people were indignant. They demanded that Jesus perform a miracle to prove Himself, despite having just witnessed His miracles of healing and provision (John 6:2; John 6:9–14; John 6:30–31). They also invoked the miracle of manna which was given to Israel in the wilderness (Exodus 16), almost daring Jesus to do something more spectacular than that. In this verse, Jesus prepares to show that this very challenge has already been fulfilled. The manna which Israel received in the wilderness was merely a material thing. It fed their bodies, but those bodies still died. Jesus' overall point to the people has been not to confuse God's earthly wonders with their spiritual meanings. The people need to seek eternal, heavenly things instead of earthly, perishable things. Here, and especially in the next two verses, Jesus will explicitly state that His ministry, and His role as "the living bread that came down from heaven" is, in fact, superior to the manna which the people saw in the Old Testament.

The manna found in the Old Testament was meant to be a prophecy of Jesus Christ. Its properties indicated the nature of Jesus: small (indicating humility), white (indicating purity), round (symbolic of eternity), and arriving at night (spiritual darkness). Manna, like salvation in Christ, could only be received—it could not be earned or made. Manna also provided the people with only two options: accept it and live, or disrespect it by walking right over it. The same choice—and only those two options—face all people when it comes to Christ (John 3:16–18).