About Paul's first letter to the Corinthians
Paul wrote this letter to the Christians at Corinth city. Corinth was a big, important, busy port in the country that we call Greece now. Most of the Christians there were
After he had left Corinth, Paul heard news about some serious problems among the Christians there. Also, the Christians at Corinth had written a letter to Paul to ask him questions about certain things. See 1 Corinthians 7:1.
So, in this letter, Paul tells the Christians at Corinth the problems that he has heard about. He tries to tell them why they are wrong about some things. Also, he answers the questions that they have asked him.