Controls can be various things in the metaverse, from UI elements to functions to events to constants. The avatar and camera can be specifically controlled through LSL but another type of control is flow control. Also, vehicles and weapons tend to have special controls (usually with mouselook and/or a HUD).
Functions
llClearCameraParams
llSetCameraParams
llReleaseControls
llTakeControls
Constants
PERMISSION_CONTROL_CAMERA
PERMISSION_TAKE_CONTROLS