A skateboard is a board with wheels on the bottom that you ride standing up. If you practice enough, you'll be able to do tricks on your skateboard, or at least ride down the block without falling off.
When you ride your skateboard, you can say that you skateboard or skate. The sport or activity you do on a skateboard is skateboarding. The first skateboards, consisting of boxes or boards fitted with wheels from roller skates, appeared in the 1940s. The earliest skateboarders were surfers who wanted a way to practice even when they were on dry land—because of this, they were sometimes called "sidewalk surfers."