Voltage (V) is the potential energy of electricity. Voltage can be present even if there is no current flow. For example, your battery can have 12 volts in it even if it's not being used. That 12 volts is still there, waiting to be used, and is the battery’s potential. Think of battery voltage like you think of a full tank of gas; it can get you somewhere, but not until you start the engine and begin to use it.
One really cool thing about voltage is that in an electrical circuit, all of the voltage the electrical circuit started with is used up when traveling through the circuit. For example, if you start with 12 volts at the battery positive and you run it through a circuit, by the time it goes through the load and reaches the negative battery post to complete the circuit, it's down to zero volts. Why is this cool? Because it allows us to do one of the best tests in electrical diagnostics: the voltage drop.