Tychicus was one of Paul's special helpers. He delivered several of Paul's letters, including Ephesisans. He explains that this letter was written to the entire church in Ephesus, and talks about several key portions of the letter.
Paul explains why he sent one of his assistants, Onesimus, back to his former owner named Philemon. He sent a special letter to Philemon explaining how he wants Philemon to react. That letter is known as the book of Philemon.