Presta valves are skinny, metal, lighter and found on high-end bikes.
Schraeder valaves are rubber, heavier, thick and found on less-expensive bikes. 700c tires and tubes are usually used on road and hybrid bikes. In addition to a tire's diameter, you must also know its width. For 700c tires, the width will typically be between 18 and 32 millimeters. English measurement system widths may also be used, particularly for mountain bike tires.