Jesus introduces two new concepts. He lays down his life for his sheep. And he knows them and they know him. He communicates with them and they with him.
"I am the gate." Shepherds at night would secure their sheep together in a compound. One man is left on duty, the others have the night off. He actually sleeps across the entry to protect the sheep from wolves. He lays down his life! In this sense, Jesus is the Gate.
Jesus says "I am the good shepherd." From our knowledge of the OT Jesus is claiming to be God. "I know mine and mine know me."