Technically, this word may be used to refer to any object which is orbiting another. However, it is most frequently used to refer to the primary vehicle component of the U.S. Space Transportation System, better known as the Space Shuttle. The Orbiter is the actual spacecraft, and as such carries a name (Endeavour, Atlantis, Columbia, Discovery). It is mated with Solid Rocket Boosters and an External Tank to produce the Space Transportation System.

Orbiter is a free space-flight simulator. It maintains a focus on realism as opposed to sci-fi, although there are plugins that betray this goal of the simulator.

Orbiter can be extended with plugins and is coded in DirectX 7 for Windows. The Orbiter website is located at http://www.orbitersim.com/.