Calisthenics is difficult to define, but in fact, it comes down to (complex) exercises where you only use your body weight. Examples of exercises that fall under this heading are burpees, jumping jacks, and mountain climbers.
Our favorite are burpees. You start with them standing up. Then you squat and place your hands flat on the ground, after which you 'kick' your legs backward, to get into the push-up position. Then you push yourself up and pull your legs back under your body. From this crouching position, you jump explosively upwards, releasing your feet from the ground. Virtually all your joints and muscle groups are involved in this exercise. From your ankle to your shoulder joint. A compound exercise pur sang.