There are some helpful comments there, but I think they're perhaps not sufficient for someone with little understanding of electricity. So I figured I'd give it my best shot. This is perhaps my first posting trying to explain physics. There's so much good stuff on the web, but I couldn't quite find what I wanted for this person, so I'll write it myself.
So I'll start with an analogy and restrict myself to the case of DC first. There'll be a quiz at the end so pay attention.
You know the "log ride" at an amusement park (as always, there's a wiki when you need one)? It's an artificial "canal"-type conduit in which you float on an artificial "dug-out" log. Basically a mild roller coaster on water.
So imagine such a ride that is flat...you never go up or down. Assuming there's nothing pushing on the water, your log would just sit there. So forget the log, and we'll just consider the water. The water seeks its own level. Here level is the potential energy of the water and it's all at the same potential.
To make the ride interesting, the ride is instead constructed with a high starting point and the water is pumped up to that point. This high water is now at a different potential and it falls because of gravity.
The analogy is that the water is similar to charges and the water's height is analogous to electric potential (measured in the familiar units of volts). The water pump is like a power supply, or, for the case of an outlet in your home, the power company. In either case, you get a potential difference. With the ride, the water is higher than the rest of the ride. With the outlet, one prong is at a higher potential than the other and therefore charges want to make it to the other prong.
- If you plug in a simple light bulb to an outlet, you're putting a load across the prongs. To what property of the ride does this correspond?
- Electrical resistance is essentially a measure of the difficulty the charges face in going to lower potential. What property of the ride is analogous to resistance?
Next time I'll discuss grounding and AC circuits within this analogy.