What is r3 on ps4 controller?

R3 on a PS4 controller refers to the right joystick button. The right joystick is used to control movement and camera angles in many games. Pressing down on the R3 button can trigger certain in-game actions or functions, depending on the game. Some games may use R3 to perform a melee attack, crouch, or sprint, while others may use it for other functions. The R3 button can be useful for accessing extra functionality without using additional buttons on the controller.