Vim is a modal editor: in different modes of vim, the same keystroke is interpreted differently.
You can open vim from the command line by typing 'vim'. If you want to learn more, then type ':vimtutor' for a relatively quick (~30 min) introduction. For help type ':help' or press 'F1'.
Small tips to survive in Vim
To insert text (and be in the insert mode): press 'i' then edit your text. To come back to the command mode press "ESC".
To save text (in command mode): press ':w'
To quit vim (in command mode): press ':q'
To quit vim without saving (in command mode): press ':q!'
To delete the line where the cursor is (in command mode): press 'dd'
Vim supports syntax highlighting. To activate it open up
and uncomment the line
" Vim5 and later versions support syntax highlighting. Uncommenting the next " line enables syntax highlighting by default. syntax on
Other text editors
If you don't know anything about vi, it is better to use nano.
TextEditor - other editors.