The mechanism behind the catapult is essentially timeless. A catapult is nothing more than a beam secured at a fulcrum, often with a bucket at one end, and a means by which to bend that beam. Tension is applied to the flexible beam, bending it away from the fulcrum. When the beam has bent to the extent desired, the tension is released, causing the beam to snap forward. Anything from a plastic spoon in a cafeteria, to a ten-meter Roman onager, can thus be considered a catapult.
Catapults were first put to military use in ancient times. Ancient Egyptians used the device to hurl stones and flaming coals at enemy positions and installations. Instead of rope, which was ill-suited to creating tension, ancient builders used animal sinew to draw the catapult's arm. Animal muscle and intestines were cleaned, dried, and braided to produce a tough, stretchable material for this purpose. Catapults rarely traveled with an army on their wheels. Due to their weight, these ancient war machines were generally either created at the site of a battle from local materials, or else carried by the army in pieces for later assembly. Ancients also recognized the need to halt the progress of the arm through its trajectory after release. To this end, a superstructure was often built around the catapult with a cross beam at the point in the trajectory where the arm should stop.
Medieval times saw few advancements in catapult technology. The availability of good-quality rope allowed builders to construct larger catapults that could deliver larger payloads over a greater distance. Also, Atila the Hun used catapults to engage in biological warfare, throwing plague-ridden carcasses over enemy fortifications and spreading the blight. With the invention of the trebuchet, though, catapults began to disappear from the battlefield.
In video games, the catapult is primarily a siege weapon. It is often too slow to fire for effective use against troops, and similar too inaccurate. The power of a catapult is generally exaggerated in gameplay. Although stones hurled from catapults were doubtlessly effective against wooden fortifications, their use against stone walls is a subject of debate.