In this passage, St. Paul is preaching concerning the virtue of humility. He begins by describing Jesus as equal with God. When Jesus was incarnate as man, he did not take the form of a king or someone important, and he didn't appear to humans in a superhuman form, but instead became a humble man from a poor family. As man, he did not try to save himself from the cross, but obedient to God's will, suffered and died on the cross. Thus you, as a Christian, should humble yourself and be obedient to God just as Jesus was. And also, you should pray to Jesus, worshipping him both because he is God and because he humbled himself to become man and suffer for you.