When a gymnast supports her body's weight on her hands, with her legs straight up in the air, she does a handstand. It takes a great sense of balance to hold a handstand very long.
You'll learn how to do a handstand in a gymnastics class, eventually even doing handstands on a balance beam or vault horse. Some yoga instructors teach handstands, and acrobatic circus performers do many varieties of the handstand. There are even dives that require a diver to start from a handstand on the diving board before plunging into the pool.