Power

Power is a term that usually means wattage.
Wattage (W) is a convenience unit to describe electricity that includes amps and voltage, multiplied together (watts = amps x volts).
Volts and amps can be traded for each other in a current, as long as the overall amount of work (Wattage), stays the same. This is often done through induction.

Power Calculations Derived from Ohm's Law

In addition to the standard definition of a watt (volts * amps), power can be calculated when only volts or amps and resistance is known: