Hi, Lasrx:
Okay, I take back what I said. Your earlier comment about paying money and being the slow one kind of lead me down the path that you may be buying a Prius for the wrong reasons.
I don't have my own Prius yet...only about a week to wait. But I have read an awful lot about it, and from what I can tell, if you're going up a hill, the ICE will drive the wheels and possibly recharge the battery too. I guess under certain circumstances (maybe a headwind, heavy payload), an uphill climb may also need help from the electric motor.
I think if you're going downhill on a freeway, the engine keeps turning, but the fuel and spark stop, and the compression is relieved...that way, the engine is already moving when it's time to apply fuel, spark, and compression again (at the bottom of the hill).
If the ICE needs help (usually during acceleration), it will drive the wheels and generate electricity for the electric motor, so both will be moving the car.
If I have misstated anything, I'm sure I'll be corrected. So check back.