I just bought the book Art of Electronics that berkman recommended and I just started reading it. I already know what voltage is but if I didn't I would have made no sense of their explanation. They say "The voltage between two points is the cost in energy (work done) required to move a unit of positive charge from the more negative point (lower potential) to the more positive point (higher potential). Why do they have to give such a complicated explanation for such a simple concept? If I was to explain voltage I'd say "Voltage between two points is the build up of charge (electrons) at one point (negative terminal) which causes current to flow to the other point (electron deficient positive terminal). Secondly they say required to move a "positive" unit of charge. Electrons are negative units of charge aren't they? Whats a positive unit of charge?? Protons? A lack of electrons? I'm studying a few different scientific fields at the moment and I have to say electronics theory is the most frustrating and complicated.