Locations

From The StarCraft 2 Wiki

Locations in the Map Editor, and in maps are areas of effect that define where things are and where things should happen on a map.

Many triggers rely on locations being set out in advance to be able to set conditions such as "'Player 1' Brings 5 'Units' to Location 'Death'", and then deploying actions such as "Kill all 'Units' at 'Death'". It can also be used to start events, or completely arbitrary things such as keeping tabs on how the players progress through a map, or start a cinematic sequence.

Locations are used for almost every condition and action in a map.

Mapmaking Navigation [e]
Basics:	Terrain | Triggers | Cameras | Variables | Object Editor | Mods | Campaign Editor | StarCraft II Map Editor | WarCraft III World Editor | Tilesets | Use Map Settings | Locations | Map | Doodad | StarCraftWire Map Database
Advanced:	Hyper Triggers