For basic text editing vi(and vim) are pretty much identical to any other basic text editor. For someone to get started with vi all they need to know is that pressing i gets you into insert mode which is like every other text editor. You can move around with the arrow keys and press escape to stop editing. To write the file press esc and type :wq "write" and "quit." or :q! if you want to quit without saving.

If you are using vim I should also point out that pressing escape and then press u to undo changes. Repeat as many times as you need. Ctrl+r will redo. (I believe vi only lets you undo one change and no redo. Correct me if I am wrong.)

This editor is on all nix systems and is quite easy to use in the basic capacity. But to each their own. I have not tried emacs lately so I cannot attest to that editor.