Teleporter

A teleporter is a device using the principle of Slipspace translocation, allowing for instantaneous transport over short distances to another teleporter or teleporter exit point. Unlike the Forerunner teleportation grid which is to transport an individual without any visible device, teleporters require a device on both ends.

Usage
The Forerunner were known to use a teleporter to transport from the Apex site to the interior surface of the shield world encountered by the Covenant and UNSC in 2531. This same teleporter appears to also transport to other parts of the interior surface, though only one teleporter is used to send things back to the Apex.

The Covenant acquired this technology to a degree in one of their countless relic-hunts, and later utilized it in Spires, large structures that could teleport forces to the ground from a ship overhead. They were used to an extent in the Fall of Reach.

Multiplayer
In the Halo games, teleporters appear mostly in Multiplayer, with the exception of Halo Wars. They are most often seen on Forerunner and Covenant structures, on levels such as Blood Gulch and Beaver Creek. In some multiplayer maps such as Elongation however, teleporters can be found on clearly human-constructed structures. This is most likely a non-canon gameplay element, as no canon source has indicated that humans would possess such advanced technology. Teleporters usually appear green, with the exceptions of Cold Storage; Citadel and Gemini, where the teleporters are blue.

In Halo 3, teleporters were present in hardly any multiplayer map because Bungie thought it was too easy to "camp" near them and get easy kills. Instead, Man Cannons took their place for the most part. Despite this, teleporters were reintroduced in the recently released map Avalanche, as well as appearing on Cold Storage. Teleporters are available, however, in Forge for every Halo 3 map. In Halo 3, when a person enters a teleporter and is going at a high speed (most likely caused by a jump from above), they keep their momentum and come out at the same speed, but in the direction it is aiming (indicated by the glowing polygon at the teleporter's base).

Trivia

 * A clever, though usually considered cheap, strategy involving teleporters is to go through one, then immediately move backwards. If the space behind it goes back far enough, then you can camp behind the teleporter.
 * In Halo: Combat Evolved, Halo 2 and Halo 3, it is possible to block the teleporters (especially in Blood Gulch) with a vehicle or by simply standing on them.
 * Telefragging is the use of a teleporter to kill somebody standing on top or inside another teleporter. The player standing on top of the "receiver node" of the teleporter will have the screen slowly turn white before being killed as a "suicide" (this only occurs in Halo: Combat Evolved, 'Halo 2, and Halo Trial, in Halo 3'' it says it is blocked).
 * In Forge, if teleporter A connects to both teleporters B and C, then if a player enters teleporter A in the opposite direction of the glowing indicator on its base, said player will be transported to teleporter B every time; conversely, if the player enters teleporter A in the same direction of the glowing indicator on its base, said player will be transported to teleporter C every time.
 * In Halo: Reach, it is possible to change what goes through the teleporter. For example, you can make it so that vehicles can go through but not individual players.