Zone

A map Zone, or "Spawn" as they are called internally by some ArenaNet members, are a technical entity in the game world of Guild Wars.

They consists of a number of variables.

A name, which is not always unique.
A region to which they belong.
A 'Terrain block' that is used as the underlying territory.
A binary distinction between staging areas and combat areas. The former are persistent, massively multiplayer and can have several districts. The latter are instanced and only contains the player characters that entered at creation of the instance.
A set of objective in some of them. (See Mission.)
A long list of entities that are to 'spawn' in them.
- NPC creatures.
- Map objects, interactive or not.
- Portals, one way of movement to another zone.

Quests can further affect the entities that spawn.

Zoning

Refers to moving into a new zone. This has the following effects:

Fully restoring Health and Energy, including the resurrection of dead party members and Animal companions.
Removing any bundle held.
Removing any skill one is under the effect of, with some exceptions:
- Morale Boosts & Death Penalty are retained when zoning between combat areas.
- Siege Devourer is retained when moving between combat areas in the Charr Homelands region.
The loss of any Minions
Recreating any instance, including rerolling any random effect, such as boss spawn.

Leaving a zone and the reentering, Rezoning, can be used to obtain any of these effects.

Entering a new zone can be done in several ways:

Entering a Portal in another zone.
Using Map travel, if the target is a staging area that has already been visited.
By choosing an option in the dialogue of an NPC. This is mostly used for entry in areas that are restricted in some way.
After a timer expires, the timer having been started by pressing an Enter Mission button, or achieving some condition in the zone, usually representing completion in one way or another. Examples could be completing a dungeon or losing an arena match.