There are two types of valves which you will frequently encounter on bicycles at the co-op. One is the Schrader valve, which you will see much more frequently. The other is the Presta valve. The Schrader valve is fatter and is identical the valves found on car tires. The Presta valve is only found on bicycles. Most pumps at the co-op will fit either, with a larger hole for Schrader and a smaller one for Presta.
The more common type at the co-op is known as a Schrader valve, and is exactly like the valve found on car tires. It's not important that you or anyone else remember the name, as anyone will understand "the fat kind" or "car valves". If you call a Schrader valve a Presta valve, however, it is unlikely that anyone will understand you. To inflate a Schrader valve, you will need to use a pump that has a slightly larger hole. On a pump that is compatible with both, choose the larger of the two.
Presta valves have a metal piece that keeps them closed which needs to be unscrewed first. It might not be clear from looking at it, but just grab the valve and make an unscrewing motion, and it should come out. This is really the only difference between the two valves. Either type may have a plastic cap on the end, so you may end up unscrewing the Presta valve twice. It is not a big deal if the piece at the end of a Presta valve is a little bent, like in the picture. Also, note the small metal nut that is screwed down to the rim on the Presta valve. If you are removing a Presta valve from a rim, you will need to unscrew this as well.
While it isn't recommended sometimes you are stuck using a gas station pump, or an older pump, which only works with schrader valves. The solution is called a presta adapter, which are presta to schrader valve converters. They just screw on to an open presta valve (rubber o-ring first) to mimic a schrader valve.