In this presentation, Jesus explains what it means that he is the living bread that results in eternal life.  There are overtones of eucharistic activities, revelatory ideas, and ways of relating to Jesus by means of this bread.  Believing Jesus and eating his flesh and drinking his blood are part of this.  Of course, the crowd does not get this teaching. 

Jesus is an ordinary man—everyone knows him, and everyone knows his father and mother.  How can someone so ordinary be living bread.  It turns out that even disciples have difficulty with what Jesus is saying.  Many of them abandon Jesus.  Only the twelve stick around.  However, Jesus points out that, though he has chosen the twelve, one of them is a devil!