Catapults
Catapults rely upon muscle or sinew tension to release a projectile. Catapults can be broken down into two basic types; those that shoot arrows, and those that hurl large stones. The smaller variations that fired arrows were more useful in field battles, while larger stationary units that hurl large stones were intended for siege warfare. While names vary, arrow based machines were generally referred to as ballista in the medieval period, while stone hurlers might be referred to as a mangonel or onager.
Early Trebuchets
The trebuchet's name is derived from the French term trebucher which means to throw over. The Latin term for a trebuchet is a ingenium, which means ingenious device. The trebuchet was introduced in Europe by the French around 500 A.D. Early traction trebuchets relied upon a troop of men to pull down the firing arm with ropes.
Later Trebuchets
Counterpoise trebuchets replaced men with a counter-balanced weight placed upon a arm, which was used to prime the throwing arm. This allowed the size of the projectile to increase greatly. Large counterpoise trebuchets typically hurled a 200 pound stone over a space of several hundred meters. The high arc created by the firing also allowed projectiles to pass over the tall stone walls to hit the defenders and interior areas of fortifications.
Obsolescence
The trebuchet and it's sinew-powered fellows were eclipsed by the rise of the cannon, which began to appear in Europe in the 1500s with regularity. Cannons provide many advantages over trebuchets including mobility, ease of manufacture and range.