Jesus has told the disciples that he is soon going to be handed over and killed. As he is preparing for his time on earth to end he seeks to comfort and prepare his disciples. He tells them that he is going to prepare a place for them in his Father's house. Once Jesus ascends, he goes and advocates to us before the Father, preparing for our entry into heaven.
One of the most well know passages is Jesus' claim to be "the way, the truth, and the life." Jesus is the way to eternal life. His death and resurrection give us a path to the Father and eternity. By confessing your sin and your need for Jesus to be your saviour you take the narrow path (Matthew 7:13) and the way to salvation. The only way to the Father is through the Son.
Jesus is the Word become flesh. The Word of God is truth and therefore Jesus is the Truth. To help us along the path he shows us how we are to live by speaking the Word of Truth to us. Jesus' life and teaching reveals the Father to us. It is only through the Truth that we can know the Father.
Jesus is also the life. We are considered dead in our sin (Ephesians 2:1) but because of Jesus' sacrifice, if we put our faith in him, confess that we need him to forgive our sins, then we are no longer in sin but in Christ. This means we are no longer dead in sin but have new life through Jesus. Jesus paid the debt of sin, death, so that we may have eternal life!
Jesus ends off with promising the Holy Spirit to come to the disciples. The disciples always had a hard time understanding what Jesus was telling them through parables and his teachings. We see this in our passage when Jesus says in verse 7 "If you had really known me, you would know who my Father is. From now on, you do know him and have seen him!" Immediately Philip asks to see the Father. Jesus basically had just told them that he has seen the father through Jesus. They needed the Spirit to interpret what Jesus was saying to them and the time was coming when that Spirit would come.