Vi is just an editor, but vim is "Vi improved", and the improvements include the sorts of programmability that Emacs is known for, which allow modes to include

Vi is just an editor, but vim is "Vi improved", and the improvements include the sorts of programmability that Emacs is known for, which allow modes to include syntax highlighting, code completion, and so on. It's not quite the same (the beauty of Emacs is that the executable is mostly a Lisp interpreter and the editor is written in the same Lisp you can write your extensions in), but close.