Power factor is the percentage of electricity that is being
used to do useful work. It is expressed as a ratio. For
example, a power factor of 0.72 would mean only 72% of your power was being used to do useful work. Perfect power factor is 1.0,(unity), meaning 100% of the power is being used for useful work.
Power factor correction, then, is the method(s) used to
fix the problems that cause power to be wasted. Energy is
saved, and penalties levied by power companies are reduced
or eliminated.