What is the on off switch for located in glove box of 1999 Mazda millenia?

There is no standard on/off switch located in the glove box of a 1999 Mazda Millenia. The glove box typically contains only storage space. If you're looking for a specific switch, you'll need to clarify what function that switch controls. It's possible you're thinking of a different location in the car, or a different model year.