The editor is divided into different modules that allow the user to customize different features of a map.
The Terrain Editor allows the user to edit the map terrain, add water and doodads (like trees) and place player units and buildings with the help of the tool palette.
The Object Editor allows the user to modify most attributes of placeable objects in the game, such as the appearance and abilities of units, buildings and items. It also allows the user to create custom objects based on existing ones.
The Trigger Editor allows users to create triggers that fire when certain events occur in the game and import their own JASS code which is much easier to most people. Built on JASS, this allows for very powerful additions to the game.
The Import Manager allows the user to import custom models, textures, minimaps, loading-screens and sounds into a map.
The AI Editor allows the user to create custom AI scripts for computer players. This is not entirely reliable and it's better to use GUI or JASS to do it.
The Campaign Editor allows the user to create custom campaigns by combining maps saved in the computer. This editor features an object editor in it as well, so multiple maps can use the same units.