It means the motor will run off either voltage, depending on how you hook the power up to it. Look for a diagram on the cover over the terminals, or on the outside of the motor.
Personally, I prefer to use 220 whenever possible.
Wiring up a 220 circuit from the panel is a fairly easy proposition, but just to be safe, get a book on wiring from your local hardware store, or ask an electrician to help you. I cannot overemphasize the importance of doing the wiring by the book, so if in doubt, ask for professional help, so you get it done correctly, and don't end up getting electrocuted, or burning your shop down.
Again, SAFETY FIRST!