Howdy!! Our official greeters seem to be slacking off tonight.

Spinning on a bike can be defined in a couple of ways:
1) Spinning classes held indoors at gym on a trainer or stationary bike
2) The cadence at which you pedal -- depending on terrain (road, pavement, hill, etc.) it changes. Roadies tend to strive for 80-90 RPM on flat pavement. By keeping the gears easy and the cadence high, you can be kind to your knees.
3) Proper pedal stroke - most easily done with clipless pedals or cages where you feet are attached to the pedal so you can use pull up and push down, though this description really over simplifies the proper stroke.

Search the forums and you'll find an overwhelming amount of info and opinions about all of this. Perhaps someone knows a particular thread which has the most succinct discussions????