Definition of the volt
Voltage = (energy/time) per (charge/time)
Conceptually the volt is the energy transferred per coulomb of charge. However the volt is in fact defined via the formula power = current x voltage:
One volt is the potential difference across a conductor when a current of one ampere dissipates one watt of power.
So instead of energy we have power, which is just energy per second.
And instead of charge we have current, which is just charge flowing past a point per second.
So the official definition is just our conceptual definition but per second. In other words it's
The energy-transferred-per-second per coulomb-of-charge-passing-each-second.
I'm sure that's a lot clearer...