The diagrams show the following:

• Figure A shows a fixed pulley, where the wheel is attached in a fixed location. Fixed pulleys are only able to rotate in place, so it can only change the direction of force, but not the size of the force being exerted.
• Figure B shows a moveable pulley, which attaches itself to the object being moved. This allows it to change the direction and size if the output force.
• Figure C shows a pulley system which is a combination of both a fixed and a moveable pulley. This one has four segments of supporting rope woven through two large wheels and two smaller wheels.