A Polar Orbit (PO) is an orbit in which a satellite passes above or nearly above Earth’s North and South poles on each revolution. It, therefore, has an inclination of (or very close to) 90 degrees to the equator. Except in the special case of a polar geosynchronous orbit, a satellite in a polar orbit will pass over the equator at a different longitude on each of its orbits. 
Polar Orbits are often used for earth-mapping, earth observation, capturing the earth as time passes from one point and reconnaissance satellites, as well as for some weather satellites. The Iridium satellite constellation also uses a polar orbit to provide telecommunications services. The disadvantage to this orbit is that no one spot on the Earth’s surface can be sensed continuously from a satellite in a polar orbit.