A sprocket[1] or sprocket-wheel[2] is a profiled wheel with teeth, or cogs,[3][4] that mesh with a chain, track or other perforated or indented material.[5][6] The name ‘sprocket’ applies generally to any wheel where radial projections engage a chain moving over it. It is distinguished from a gear in that sprockets are never meshed together straight, and differs from a pulley for the reason that sprockets have teeth and pulleys are easy.
Sprockets are found in bicycles, motorcycles, vehicles, tracked vehicles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear movement to a monitor, tape etc. Probably the most typical form of sprocket could be within 
the bicycle, where the pedal shaft bears a large sprocket-wheel, which drives a chain, which, subsequently, drives a little sprocket on the axle of the trunk wheel. Early automobiles had been also largely powered by sprocket and chain system, a practice largely copied from bicycles.
Sprockets are of varied designs, a maximum of efficiency being claimed for every by the originator. Sprockets typically do not have a flange. Some sprockets used in mixture with timing belts possess flanges to keep the timing belt centered. Sprockets and chains are also used for power transmission in one shaft to some other where slippage isn’t admissible, sprocket chains becoming used sprockets instead of belts or ropes and sprocket-wheels instead of pulleys. They could be run at high speed and some forms of chain are so built concerning be noiseless even at high speed.