Servos can be used for lots of things where a great detail of control is needed such as steering RC vehicles, robotics and freaking out small children with moving dolls. Standard Servos like the one provided by Oomlout travel through 0 to 180 degrees with positioning controlled via a timed pulse. Timing varies with manufacturer but for example a pulse sent every 25 to 50 ms will run the servo smoothly.
Arduino comes with a built-in Servo library that can be used:
or you can write your own which is slightly more complicated but allows you to understand how the pulsing works. I found that the values given by the documentation didn’t quite match up.