Why Power is the rate at which electrical energy is used or produced, and its unit is the watt. In a DC circuit, power equals voltage times current (P = I x E), so 12 volts at 2 amperes is 24 watts. Volts measure electrical pressure and amperes measure current flow, but neither alone tells you the rate of energy use.
Watch out Watt-hours is the tempting one, but that is energy: power multiplied by time, which is what an electric bill measures, not power itself.
Watt = rate now; watt-hour = amount over time. Power questions want the plain watt.