I begin with a brief description of the insert mode because it is very straight forward. In insert mode the characters you type are inserted into your document. You can use the backspace key to delete any typing mistakes you have made on the current input line. The escape key (<esc>) takes you out of insert mode and back to the command mode. If you are ever in doubt about what mode you are in, just press <esc> a few times until vi starts complaining. You will then know that you are in the command mode.