I know the importance of shoes - running shoes, that is. Most track runners own at least two pairs, some trainers to practice in and spikes to run races in.
Trainers are pretty much your standard sneaker, but they can get a lot fancier than that. Most of them have extra padding in the sole, which increases the time of impact between your foot and the ground. This means the impulse in your leg is much less, causing less injury to the runner.
Running spikes have much thinner soles, which can be good and bad. They're not very healthy to wear all the time, since running in them puts greater impulse on your feet and joints. But since they're so much lighter, they take less energy to lift off the ground - energy you can save for the finish line.