A sprocket[1] or sprocket-wheel[2] is a profiled wheel with tooth, or cogs,[3][4] that mesh with a chain, track or other perforated or indented materials.[5][6] The name ‘sprocket’ applies generally to any wheel where radial projections engage a chain passing over it. It is distinguished from a gear in that sprockets 
should never be meshed together straight, and differs from a pulley in that sprockets have teeth and pulleys are easy.
Sprockets are found in bicycles, motorcycles, cars, tracked automobiles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or even to impart linear movement to a track, tape etc. Maybe the most common form of sprocket could be within the bicycle, where the pedal shaft bears a sizable sprocket-wheel, which drives a chain, which, subsequently, drives a small 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 varied designs, no more than efficiency becoming claimed for each by the originator. Sprockets typically do not have a flange. Some sprockets used in mixture with timing belts possess flanges to keep carefully 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 being used rather than belts or ropes and sprocket-wheels rather than pulleys. They could be run at high speed plus some forms of chain are so built concerning be noiseless actually at high speed.