Like Ljusdahl said, it's the trigger like you probably make them in the trigger editor. What World Edit does is, when saving, compiling (converting) the GUI into Jass, the programming language of the triggerfunctions. Some people don't use GUI and just use jass without having to compile their triggers into jass because it already IS written in jass. Why do they write it in jass? because some things simply can't be done in GUI, and some things can be done better in jass than in gui.
Someone who never used WE but has played warcraft might understand a GUI trigger, because it's quite easy to read. Someone who has never seen jass before (or any other high level programming language) probably does not understand it.