This is a picture of the one gear that is on the bike, and is where the bike gets its name "single-speed."
Above is another type of bike that I have called a cyclocross bike. This bike is used for gravel roads, paved roads, or even off roads. One of the things I like to use this bike for is cyclocross racing. These are quick races that are usually held in parks where the coarse consists of miniature hurdles, a huge hill to climb up, and on and/or off road paths. They separate racers up into age groups and when they start the race you go as fast as you can where you ride as many laps that you can get in within a half an hour, and see who is the best racer physically and mentally to be able to pull away from the rest and come out with a win.
These races are held in many different types of weather conditions, where if it's raining, snowing, sleeting, or windy, the race will still continue. The more mud the better!
This is a picture of the hurdles where the racers will dismount, throw their bikes over their shoulders, and jump over them, or if you're good enough, bunny hop over like Nate Woodman above, who is the only one in the state who can perfect such a tough maneuver.
Cyclocross is such a great way to get outside to test your skills, and to be able to view biking from a different perspective. I have enjoyed biking for many years, and this sport and hobby is something that I will be able to cherish for the rest of my life.