These steppers have a threaded shaft, which allows them to be used as a linear actuator. As the motor runs, it moves along the shaft at a specific rate of 1cm per 5 full rotations. These are a good choice for linear motion where precision and repeatability are important.
Note: It looks like the datasheet for this stepper may not be accurate. When connecting this motor to a bi-polar driver you'll want to wire it according to the wiring diagram in the documents below.