Do you know what a bicycle is? It's a way to move your body to make the bike move. A human-powered land vehicle is like that, but it can be all kinds of things like a tricycle or a scooter.
You use your muscles to pedal or push and make it go forward or turn. It's like when you push your toy car or ride your scooter in the park. But instead of using a motor or electricity like in a car or bus, it goes by using your own power.
It can be really fun to ride and it's also good exercise for your body!