"Paul, a prisoner of Christ Jesus, and Timothy our brother, To Philemon our dear friend and fellow worker," NIV translation
This letter was written by Paul while he was under house arrest in Rome. He introduces himself and reminds us that he was there by the will of God and that it was not by the will of men. The letter is addressed to a dear friend that came to Christ while Paul was teaching in Ephesus. This friend was a rich man that lived in Colosse and had went to Ephesus to hear Paul teach.
"to Apphia our sister, to Archippus our fellow soldier and to the church that meets in your home." NIV translation
The letter was also addressed to his wife and son as well as to the group of believers that met in their home. It is hard for us to understand today as we see huge places of worship all over the place but, in the early days, they did not have dedicated buildings for worship so they met in homes.
"Grace and peace from God our Father and the Lord Jesus Christ." NIV translation
This was Paul's usual formal greeting that he opened his letters with. He always put grace before peace as a reminder that it is only by grace that we have peace with God.
"I always thank my God as I remember you in my prayers, because I hear about your faith in the Lord Jesus and your love for all the saints." NIV translation
Paul always prayed for the individuals and groups of believers that he had brought to Christ. Here, he lets us see what he prayed and he starts by thanking God for his faith and love for the saints. Paul had heard about his faith and had evidence of it in his love for fellow believers.