Galatians was written by the Apostle Paul to the churches of Galatia.
Galatia refers to the central region of modern day Turkey, and the churches Paul is writing to are most likely the churches he started on his first missionary journey.
Written probably sometime around 54-57 A.D.
Paul wrote Galatians combat the idea that Gentile Christians had to keep the Old Testament Law (especially the visible marks of the Law such as circumcision and sabbath keeping) in order to be justified and part of God's people. For Paul this idea is a perversion of the gospel and he's quite fired up when he writes this letter!
Click the links below to listen to the commentary on that section.