Calisthenics is exercise, like jumping jacks or pull-ups, that people do to stay in shape or get in better shape.
Doing calisthenics usually involves simple movements, like stretching, jumping, bending, and kicking, that don't involve a lot of equipment, if any. Kids in gym class do calisthenics, and calisthenics are helpful to many people, including athletes and people in the military. The push-up is a famous example of calisthenics. Those limber folks on cheerleading squads are masters of calisthenics. A little calisthenics can be helpful in anyone's everyday routine as a way to build endurance and stay healthy.