Mark,
Have fun up north.
Glenn,
The MOSFET is like a transistor in that it can act like a switch or an amplifier, but is uses a Voltage to control it and the transistor uses a current. The MOSFET needs to exceed a Voltage of about 3-4V across two of its pins before it ever turns on. Once the two pins reaches 3-4V any more Voltage would result in an increase in current. That is kind of the simple version my school talked about. The MOSFET is better than a transistor in high current circuits, since it is easier to control and is more efficient.
Nick