Book of Philemon is also the name of a person, Philemon.

Does Christian brotherly love really work, even in situations of extraordinary tension and difficulty? Will it work, for example, between a prominent slave owner and one of his runaway slaves? Paul has no doubt! He writes a "postcard" to Philemon, his beloved brother and fellow worker, on behalf of Onesimus--a deserter, thief, and formerly worthless slave, but now Philemon's brother in Christ. With much tact and tenderness, Paul asks Philemon to receive Onesimus back with the same gentleness with which he would receive Paul himself. Any debt Onesimus owes, Paul promises to make good. Knowing Philemon, Paul is confident that brotherly love and forgiveness will carry the day.

Since this letter is addressed to Philemon in verse 1, it becomes known as Pros Philemona, "To Philemon." Like First and Second Timothy and Titus, it is addressed to an individual, but unlike the Pastoral Epistles, Philemon is also addressed to a family and a church (verse 2).