Calisthenics is a system of physical exercises that uses only one's own body weight. It originated in Ancient Greece and has a history of being used by Spartan warriors and Shaolin monks to build strength and combat skills. Calisthenics exercises can be done anywhere, though some require access to a high bar. There are basic, static, and dynamic exercises that target large muscle groups through movements like pushups, pullups, and exercises that maintain challenging positions. Benefits include not needing equipment or gym fees, while the main drawback is potential issues working out in rainy weather.