Schrader valves are very commonly used on cars and motorcycles, as well as most entry-level bicycles. They have larger threads and a small pin which can be depressed to release the air pressure.
Presta valves are generally used on high-end bicycles. The air release pin is built into a small, threaded stem which can be locked down to prevent air from unintentionally escaping or loosened to allow easy depressurization.
