The LB (Left Bumper) and RB (Right Bumper) buttons for the Xbox Series S and Xbox Series X controllers are the keys located on the top side of the controller, next to the triggers (LT and RT), and are often used for various actions and functions in the game, such as weapon switching, defensive moves, or other shortcuts.

These buttons are essential for the majority of games, and their proper functioning is necessary for a comfortable and complete gaming experience. The LB and RB are also designed to provide quick and accurate response, as players often use them for rapid actions or in combination with other controls.