An orrery is a mechanical model of the solar system, traditionally with gears and arms attached to spheres representing the Sun, planets and perhaps moons, designed to move them with the same relative motions as in the actual solar system. The spheres are often using a different scale than the orbits, and may not be in scale with each other: the relative sizes and distances make using a single scale impractical. Mechanical orreries using clock technology have been built for centuries. (The word orrery comes from the place name Orrery in County Cork, Ireland: an Earl of Orrery was recipient of such a mechanical model.)
The term has been borrowed for software or videos that display such motions on a screen, particularly for those showing models of other planetary systems, often created showing more than one system on a single screen. A series of such video orreries showing Kepler Telescope discoveries (Kepler Orrery I, II, etc.) have displayed summaries of Kepler discoveries, simultaneously showing numerous planetary systems with their orbital motions, shown next to each other on the screen.