Riding switch is the opposite of what your rider is used to. If you have a regular stance rider, then switch would be the goofy stance for them, and vice versa. When you do switch tricks, you get more points than what you would normally get for doing it in regular/goofy form. For example, doing a Kickflip (regular) results in 100 points, but a Switch Kickflip gets 120 points. It makes a larger difference on bigger tricks such as specials.