This library allows you to control unipolar or bipolar stepper motors. To use it you will need a stepper motor, and the appropriate hardware to control it. For more on that, see Tom Igoe’s notes on steppers.
See the circuits from the Arduino reference:
Refer to the example from the Arduino tutorial:
The text of the 86Duino reference is a modification of the Arduino reference, and is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.