The jam serve (AKA wrap-around serve) is a unique serve used in both singles and doubles. The goal of this serve is to have the first bounce of the ball hit the floor in the center of the court, but as close to the back wall as possible.
In singles, use it against opponents who have trouble pivoting quickly on their feet or who stand too close to the back wall.
In doubles, use it to split the receiving team and wrap around the right side receiving player.
Ben Croft provides a short lesson on how to take a shot off the back wall. He suggests using your racquet or hand to find the back wall, and then to move forwards, building up momentum before hitting the ball.
This Malia Bailey video covers the most basic racquetball strategy to always move to center court position. The player who can best control the center court position will most likely win the rally. If you are hitting from the back of the court, then your goal is to move your opponent to the back wall with a ceiling ball or a passing shot.