L and R in controller refers to the left and right bumper buttons on an Xbox One or PlayStation 4 controller. The left bumper button is typically used to control the player's left hand, while the right bumper button is used to control the player's right hand. In some games, the left and right bumper buttons may be used for different purposes. For example, in first-person shooters, the left bumper button may be used to aim down sights while the right bumper button may be used to fire the weapon.