The phrase "right stick" refers to a small control stick or joystick that is located on the right side of a video game controller. It is used mainly to control the camera or aim in a game. Full definition
A fairly standard design choice; you can also turn your head to turn the rig, though that can also be accomplished with the usual right stick. (newgamenetwork.com)
Combined with the zero gravity nuance, this is a finicky combination that can produce a fair bit of discomfort (with right stick movements restricted, zero gravity movements a full 360 degrees). (impulsegamer.com)