A Stargate is a ring-shaped device of Ancient manufacture in an intergalactic network of such devices which allow near-instant travel over interstellar distances via wormhole. The primary Earth stargate is operated by the US Air Force at Stargate Command.
Stargates are made of naquadah, a superconducting material that stores the energy required to form the wormhole. To connect to a remote location, a charged stargate "dials" its address combination with seven of the nine chevrons on the outer ring and the thirty-nine glyphs on the rotating inner ring. When the stargate locks onto a valid location, a large destructive "whoosh" appears momentarily, and is replaced by the shining water-like surface of the wormhole.
Many remote stargates have a "dial-home device," or DHD, to charge, dial, and activate the Stargate. The Stargate found in Egypt did not have a DHD, and it took the scientists years to MacGyver a solution.
A stargate network is a set of stargates intended to interact with each other. Usually there is one stargate network per galaxy. Stargates in different galaxies often are generally visually distinguishable from each other.
Under normal conditions, a pair of Stargates can not stay connected for more than 38 minutes.
There can be only one active Stargate per solar system. Only one of the two Earth stargates could be active at one time.
It is possible to build a functional Stargate out of Terran electronics with proper information, although such a Stargate is only good for one trip.