Ever hear anybody talk about their "cadence" when they ride? Cadence refers to the speed at which a person twirls their pedals when they ride. Having a high pedal cadence is a good thing, since (generally speaking) the faster you can spin your pedals, the faster you can go on your bike.
Having a high cadence means you're spinning the pedals as opposed to mashing on them. Higher pedal RPMs generally means you can ride longer without getting tired, since the idea is to spin the pedals more quickly at an easier gear, rather than burn through all your leg muscles pounding away in a much more difficult gear.