Switch eh? Well they don't come much simpler than this. Switch is standing in the opposite stance to your usual. If you normally skate goofy, skate regular, and vice versa. This is done usually when you have a lot of tricks down and you want more of a challenge.
You are also going to need to be able to switch round to the opposite stance whilst moving this is to correct your footing after a trick or prepare for a fakie trick.