A sprocket[1] or sprocket-wheel[2] is a profiled wheel with the 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 upon which radial projections engage a chain passing over it. It really is distinguished from a equipment in that sprockets are never meshed together straight, and differs from a pulley in that sprockets have tooth and pulleys are smooth.
Sprockets are used in chain sprocket 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 carries a big sprocket-wheel, which drives a chain, which, in turn, drives a little sprocket on the axle of the trunk wheel. Early automobiles were also largely powered by sprocket and chain mechanism, a practice generally copied from bicycles.
Sprockets are of various designs, no more than efficiency getting claimed for each by its originator. Sprockets typically do not have a flange. Some sprockets used with timing belts possess flanges to keep carefully the timing belt centered. Sprockets and chains are also utilized for power transmission in one shaft to another where slippage is 
not admissible, sprocket chains becoming used instead of belts or ropes and sprocket-wheels rather than pulleys. They can be operate at high speed plus some kinds of chain are so built as to be noiseless actually at high speed.