Power means multification of Voltage and current.

power=V*I, Voltage is electric potential energy per unit 
charge, measured in joules per coulomb ( = volts). It is 
often referred to as "electric potential", which then must 
be distinguished from electric potential energy by noting 
that the "potential" is a "per-unit-charge" quantity. Like 
mechanical potential energy, the zero of potential can be 
chosen at any point, so the difference in voltage is the 
quantity which is physically meaningful. The difference in 
voltage measured when moving from point A to point B is 
equal to the work which would have to be done, per unit 
charge, against the electric field to move the charge from 
A to B.

Power is the energy utilized in a particular span of time.
Calculation of power depends on the type of energy utilized.

Power is nothing but the rate of doing work.
In electrical engg., u can say it is the rate of change of 
stored energy. Usually in EE,instantaneous power is given 
by product of Instantaneouw V and I.

Power is rate of change of Workdone. P= (W/t)
SI Unit - Watt
Dimension : M1 L2 T-3

Multiplication of voltage and current of specific load. 
It can be either watts or voltampere.