Switch means rolling in your opposite stance. Switchstance
At first skateboarding was done in your natural stance. Like handwriting with the right or left hand we skate better in a certain stance. Regular skaters ride with their left foot forward. Goofy skaters ride with their right foot forward. There are other stances but that is the main ones.
In the late 80's skaters on the streets started skating in their switch stance. Doing so increased the difficulty of the tricks they were doing. Switchstance skating became a measure of how good a skater you were. If you could skate switch then your were pretty good. The same holds true today. Switch is the short form. Switch tricks are done from the back or tail of the board while rolling.
Try any of your regular tricks switch.
Riding switch will double your skateboarding ability. It will feel unstable at first. Just keep trying and it will get easier.
Roll switch. Push switch and get used to the balance.