A pulley on a flagpole is an example of a fixed pulley. This kind of pulley has a wheel with an axle attached to a support structure, as in this case, the flagpole.
With fixed pulleys, the force needed to raise a load is equal to the force of gravity pulling the load weight downward. This is the simplest type of pulley and offers no mechanical advantage by itself.
Other types of pulleys include movable pulleys and compound pulleys. A movable pulley has the wheel and axle directly attached to the load, while either end of the rope is pulled upwards from the load. Simple movable pulleys have a mechanical advantage of two. A compound pulley is a combination of fixed and movable pulleys. This type offers the greatest amount of mechanical advantage.