RPM stands for Revolutions Per Minute. It is a measure of the frequency of rotation, the number of revolutions per minute. It tells how many times a mechanical component revolves around its axis in one minute. So, RPM is the rotational speed of a mechanical component such as the crankshaft of an engine, power generator turbine, CD or DVD player and turbocharger.

A common example to understand the RPM is the tachometer in the dashboard of a car. It shows the frequency of rotation of the engine. It measures how many times the crankshaft of an engine revolves around its axis in one minute. Generally, a tachometer measures RPM in thousands so if its needle is at 2 it means the engine is at 2000 rpm and its crankshaft is revolving 2000 times in one minute.