LEO (Low Earth Orbit) is an acronym that refers to the orbital zone just above the earth atmosphere, it starts about 170 km and extends to roughly 500 km.

An object in LEO has a velocity of about 7.6km/s, about 68% of escape velocity. However, an object in LEO is continually fighting the last vestiges of the atmosphere and will eventually reenter, typically after just a few orbits at 170km or centuries at 500km, (somewhat dependent on the aerodynamics of the body and its density).