A catapult is an example of a third class lever.
The different classes of lever are based on the relative locations of the fulcrum, the load and the effort.
A see-saw is the classic example of a first class lever, in which the fulcrum is between the load and the effort. This is also seen in a pair of scissors.
A second class lever has the fulcrum at one end and the effort is applied at the other end. The load is in the middle. Think of a wheelbarrow. This lever is generally designed to allow very heavy loads to be moved with small efforts.
The third class lever has the fulcrum at one end, and the load at the other end. The effort is applied between these two.
A third class lever is often designed to use an effort to create high speed in the movement of the load. A fishing rod is another example of this type of lever.