Stanley is an overweight kid with a lot of bad luck. He is accused of a crime he did not commit and is sent to Camp Green Lake, the juvenile detention center
The main problem/conflict in the book Holes was that Stanley was sent to prison for something he did not do, and it was resolved when he helped shut down Camp Green Lake.
Stanley's friendship with Zero make the other boys mad at the camp and the fact that Zero digs part of Stanley's hole makes the other boys jealous. This leads to mounting tension between the boys, which eventually erupts in a fight, causing Zero and Stanley to run off.
The falling action in holes is that when Stanley and Zero come back to the camp and his lawyer comes to retrieve them only to find them in a hole full of yellow-speckled lizards.