Specifically, part of the question states:
"The electric field at all points between the electrodes is equal to the electrode voltage difference divided by L"
I always thought that Voltage is the same as potential difference, and potential difference is just the difference in potential energy between two different points in space. Same idea with gravity, where you would have obviously more potential energy higher up, then you would lower down, closer to the surface, which is your point of reference. So when they say "voltage difference" is that the same as saying just "voltage"?