There can be multiple answers to this question so I tried to give you them.
One could be Joule (J) is the MKS unit of energy, equal to the force of one Newton acting through one meter.
The next could also be a Watt, which is the power from a current of 1 Ampere flowing through 1 Volt.
And 1 kilowatt-hour is the energy of one kilowatt power flowing for one hour.