Because it's hard to know when you're going to get a flat, it's always good to have extra tubes on hand. Specialized's Airlock Self-Sealing Tube seals small punctures so you can keep riding.
Schrader valves are identical to those found on car tires. These valves are generally used on hybrid and children's bikes. Presta valves, which are found on most road and off-road bikes, are longer and thinner and feature a threaded tip, which must be opened to inflate (turn counterclockwise).