vi: the “visual editor”, standard Linux and Unix editor
vim: the “vi improved” standard Red Hat editor
On Red hat operating systems, the vi command invokes vim
Derived from earlier Unix editors

To start vim : vi filename 
If the file exists, the file is opened and the content are displayed
If the file doesn’t exists, vi create it when the edits are saved for the first time

Command mode
Cursor movement
Change, delete, yank, put
Insert mode
Type in new text
Return to command mode with <ESC> 
Ex mode 
Configuring, exiting, saving
Search and replace 

//TODO complete