what does tom learn in this book

I think Tom matures in the book. Although still on the mischievous side, he learns the meaning of friendship. He becomes close to Huckleberry Finn. Tom also learns that doing the right thing has its own rewards. He exposes Injun Joe at his own peril and saves the Widow Douglas. This escalates Tom's status from a wayward orphan to a town hero. Tom, for better or for worse, conforms to societal expectations after his adventure. He is more serious about "civilized" institutions like school and church.