Gears are like linkages, transferring one motion to another. Gear wheels have teeth around the edge which mesh with the teeth of another gear. Gear wheels may also be linked by chains or belts. Gears are used as force multipliers or reducers to make things go faster or slower. They are used on bikes, cars, hand whisks, salad spinners, toys, bottle openers and even pedalos ;). Examples of some are chain and sprocket and rack and pinion. Gears can reduce the applied force needed to cycle uphill by raising the rate at which you have to pedal. A rack and pinion linkage can be used in cars to convert the rotary motion of the steering into lateral movement of the wheels similar to the tiller on a pedalo and the paddles.
A pulley is a wheel with a groove around itthrough which runs a belt. They are used to control how fast something turns. Pulleys are also used to make lifting easier. Other examples of pulleys are in cassette recorders, washing machines and cranes.
1. When there is a big wheel and a small wheel on a belt - the big one rotates more slowly than the small wheel but with greater force.
2. A twistr in a belt (pulley) makes the wheels turn in the opposite direction.