What Does The Catapult Do?

Answer 1

The catapult was usually used to fling large, heavy objects across a large area. The usual target back then was a castle when they would try to siege or surround it.

How they worked depended on the exact construction. To sling an object, the main arm has to have some sort of resistance against it as it moves over a pivot point (fulcrum). Slinging the arm could be accomplished by using a "spring" of sorts, or for the time period they were used, likely tree limbs. Even the lever itself could act as a spring. Or alternatively, heavy objects could be dropped onto the short end of the lever, sending the projectile flying.

For a crude design, they could use a tree branch, either on a tree or in a heavy frame, bend it back with the object, which is lighter than the strength of the branch and hold the end of the branch down or back with ropes. Then once the rope is slipped loose, the object flies in the direction of the target.