Base

For bases in fictional context, see military base.

A base is a generic stronghold in campaign and multiplayer. A base may be a building or a certain area, and its importance may vary depending on a mission or game.

Usage in multiplayer

Usage of bases usually varies depending on a mission or multiplayer gametype. Usually, a base is used to provide protection, or contain stronger weapons or equipment.

Throughout the Halo series, these bases may contain:

Power ups and/or Active Camouflages.
Spawn points to keep away from enemy fire.
Ammunition.
Sniper rifles.
Protection.
The Flag and flag capture points in CTF.
The skull in Oddball.
The Bomb spawn and arming points in Assault.
Vehicles (on and/or around).
Teleporters to get to various locations in the map.
Health Packs in Halo: Combat Evolved.
Turret(s) either inside, around, outside, and on top
Scenery depicting whether the base is a Red Base or a Blue Base like the team color's Flags surrounding the building and/or Red/Blue lighting.
Camping spots for snipers and/or ambushes.
Grenades.
Barricades for the Infection gametype in Halo 3.
Hiding Spot for the VIP in the VIP gametype.
Defensive positions during an attack.
Man Cannons for quick transportation.
Equipment
Territories in the gametype Territories
Grav Lift(s) to go into to go around a base's different levels
Use for cover in King of the Hill.
"Turtle" into which means to make a whole team go on defensive.
Use control panel(s) to open obstructions like gates or blockades
Supplied to be used as fortresses

Although bases are mostly used for CTF, they can be particularly useful in Oddball (to hide in, if nav points are disabled) and King of the Hill. Bases range from small rooms all the way to a huge tower with mini buildings. For example, in the map Infinity, one team also has a sub-base, quarter way to their destination.

Trivia

The only map in which both bases are literally symmetrical -- including the whole map and the level geometry -- is Rat's Nest. If exact geometric symmetry isn't required for bases to be considered "symmetrical", however, then many other maps have symmetrical bases.