As far as I know
vi is more commonly found on out-of-the-box unix systems while
vim often has to be installed. Also
vim stands for
vi improved, but improved how?
What are the main differences?
Vim tries to resemble the syntax and semantic of Vi command as much as possible. But being an "improved version", Vim adds new commands and features. It also changes the semantic of some Vi commands to better match the current expectations of its programmers.
A detailed list of changes between vim and Vi can be found using the command
Vim is an advanced text editor that seeks to provide the power of the de-facto Unix editor 'Vi', with a more complete feature set. It's useful whether you're already using vi or using a different editor.