For example, there are a set of commands that move the cursor in different ways (beginning of line, end of line, first line, last line, line #x, next word, previous word, etc. (that's ^/$/gg/G/g#/w/b) ), and a set of commands that performs actions (copy, cut mostly (y/d)). The real magic is how the two sets interact.
I don't have to memorize the sequence of keys to delete a word; I know the key to cut (d), and the key to move a word forward (w). I press d, then w, and the word is gone! It's a whole world of editing possibilities.
My secret shame: since I use GUI vims almost exclusively, I've never developed the muscle memory for hjkl movement; I use the arrow keys. When I started out, I knew i, esc, and that, and I figured out the rest as I needed it.
There's got to be a better reason to use vim than this. I mean...the standard for every other editor is ctrl-shift-left arrow, then the delete key and the word is gone! Whoopee.
It works in most editors, even Microsoft notepad and this textarea I'm typing in right now. I use unfashionable, clumsy old eclipse most of the time and could probably list 100 important things it does that vim never could. Things that actually matter. Maybe I'm wrong, but I doubt vim can launch and debug and continuously deploy to Apache tomcat. That sort of thing.