A catapult is a simple machine that uses stored energy to launch objects into the air. It works by using a lever system, where a long arm is pulled back and then released, sending a projectile flying. Catapults were commonly used in ancient warfare to hurl stones or other projectiles over walls and into enemy territory. There are different types of catapults, including the trebuchet and the ballista. The trebuchet uses a counterweight to launch its projectiles, while the ballista resembles a giant crossbow. Today, catapults are often used in science experiments and educational demonstrations to teach principles of physics and engineering.