It highlights all types and structs documented on the sc2mapster API docs. It even highlights all the constants documented as well.
If you've never heard of Vim before, it's a powerful text editor that emphasizes the use of the keyboard over the mouse. All movement commands are done in a mode which is separate from the input mode. I'm not going to go much into it here, those who swear by it will find this galaxy script syntax highlighter very handy: