Nearly everyone serious about using Linux encounters vi at some point, some without even realizing it.
The vi editor is the weird almost-empty screen or window which seems to be an editor but won't let you 
do anything, including quit, as far as you can tell. 

It's a powerful tool, but also a cryptic, almost unintelligible one. Here are five quick operations in vi
to save your skin, and perhaps even allow you to use it a little! 

1: Press ESCAPE 

For reasons which will become obvious in just a minute, the safest and most useful thing to do in vi is
to hit the ESCAPE key over and over again very often. This is because ESCAPE will return you to command
mode. For more details on what this means, bear with me and proceed to #2 and #3 below. 

2 and 3: Insert and Append 

The vi editor is a line-oriented editor which operates in two modes, either "command" mode (during which
you are talking directly to vi) or "edit" mode (during which you are talking through vi directly into the
buffer). 

To input text into a document, make sure you are in command mode by pressing ESCAPE a few times, and then
do the following: first, use the arrow keys to position the cursor near the spot where you want to insert
the text. Then, hit either 'a' to "append" text to the end of the line, or 'i' to "insert" text at the
cursor. 

After hitting either 'a' or 'i' you're free to add or insert text on that line. To stop adding or
inserting text and return to the command mode (necessary to issue more commands), press ESCAPE. 

4: Unconditional Save 

To save your document as it is, press ESCAPE (to ensure that you are in command mode), and then type: 


  :w!

This will write the file to the disk. It's not easily reversible, so make sure it's what you really want
to do! 

5: Unconditional Abort 

To quit vi unconditionally, press ESCAPE (you guessed it), and then type: 


  :q!

If you've made changes to your document that you'd like to keep, be sure to save first (see #4) before
exiting this way! 

Further help? 

For further help, see: 


  man vim

Or, if that doesn't work, try: 


  man elvis

Yes, even viewing the vi manual page is a counterintuitive process. Still, some help is better than none.