Paul was one of God's religious teachers. God sent him to preach to the people of so many different countries. Titus was a young-man, who stayed together with Paul in Jerusalem.
Paul wrote this letter about 30 years after Jesus' death and rising to life. Titus and Paul went to an island called Crete in order to spread God's good news. The island called Crete is in the middle of the sea (south of the countries of Greece and Turkey). Paul having said to Titus, “You stay here in order to help the believers (lit. devotees)”, from the island of Crete he went to a different place.
On that island there were [people] who had recently (lit:new new) come to faith. So, for them, what kind of leaders and how to choose them, Paul wrote to Titus in this letter.
Apart from these people there were also many false religious teachers there. Don't listen to false teachers like them and having warned them, stop their teaching like-that Paul said.
Paul told Titus to teach those who put their faith in God, in what way and how they should live. In this book it is saying that those who walk according to God's desire will get eternal life in heaven.