'Normal' mapping is the case where moving the joystick/mouse/analogue stick 'up', results in the game point of view shifts 'up'. The y-axis inversion control scheme is basically the inverse of this. 'Up' points the camera 'down', and 'down' points the camera 'up'. Y-axis inversion is the way that I've learned to play any game that requires change one's point of view.
Inversion of the y-axis was never really a choice me. Like many, I learned to play like this because the first games I played were flight simulators or space combat games like Wing Commander. In real-life, airplane joystick controls by default are 'inverted'. When I transitioned to first-person shooters, the mentality of the flight simulator stuck with me through the first-person view point (as well as third-person view point games).
The way that I see it, y-axis is a valid way of thinking about pointing a camera. If you imagine your virtual character as a puppet facing away from you with a pole sticking out of its head horizontally, you can make the puppet look up by tugging the pole down, and vice versa. And a similar logic applies to the flaps of an airplane, where one pulls the joystick downwards in order to 'pull up' the plane.
Inverting the y-axis doesn't really offer an advantage or disadvantage. Rather, it's just a way that some people expect controls to work in a game. And developers know this: almost every single game that has come out in the last 10 years supports y-axis inversion. However, there are a select few titles which do not, and this is why I've created the list. I hope this is a useful resource for you. Inverted gamers unite!
