All Mountain Bike Parts Descriptions

#9) Bike Tubes - Air support for your tires.
  They come in a skinny valve style known as "Presta", or a car style one called a "Shraeder". If your spare tube is a Shraeder valve and your rim uses a Presta style you will not be happy, the valve won't fit. That's why most people drill the rim hole out to fit the Shraeder valves, that way both styles of tubes will fit. Some tires don't use tubes, known as "Tubeless", but seem to have more leaking air issues then tube style tires.

Bike Parts Diagram