It has to do with the width of your rims. What type of bike are you riding now? Is it a mountain bike? A hybrid with thicker/wider tires? Please look at the sidewall of your tires and post the tire size. It will probably be 26" x something. Maybe it will say 700c x something, but given your description, it's probably 26.

The 26" is the diameter of the tire. The "something" is the width.

Higher pressure tires have less rolling resistance, meaning you don't have to work as hard to go the same speed and distance. Higher pressure tires are typically narrower, which mean that there is less friction, which also means you don't have to work as hard to go the same distance. It often means you can go faster, too, but that depends upon your physical condition and cycling skills, too.