Vim is primarily used by programmers.
Vim is widely popular because it allows users to do many functions on a document (save, search, scroll, etc.) by pressing as few keys as possible. However, the counterargument to this made by people who don't like Vim is that many of these keystrokes are confusing and don't make sense.
There is an Internet turf war between programmers that prefer Vim and programmers that prefer Emacs, another common text editor.