LEO stands for Low Earth Orbit. Low Earth Orbit refers to an altitude range of around 100-2000 kilometers (62-1240 miles) above the Earth's surface, within which a number of artificial satellites and other spacecraft operate.
Low Earth Orbit is a relatively close range to the Earth's surface, and is within the Earth's protective magnetic field. As a result, it is an important region for a variety of aerospace applications, including satellite communication, Earth observation, and space exploration.
There are many different types of spacecraft and other aerospace systems that operate in Low Earth Orbit, including communication satellites, Earth observation satellites, and scientific research satellites. Low Earth Orbit is also an important region for the operation of the International Space Station and other human spaceflight missions.
Low Earth Orbit is sometimes abbreviated as LEO, and it is also sometimes referred to as the "near-Earth environment."