A UNIX Text Editor VI is a powerful UNIX text editor. It has more advanced features than Pico and offers a variety of formatting and navigation options. Each mode is used for a different type of editing task. In different modes, the same character typed at the terminal may have different meanings.
Tasks done in command mode include moving around the text, deleting, copying, cutting and pasting.
In addition, you can get to the other modes from command mode, and you may return to command mode from the other modes as well. When you are in command mode you will not see the actual letters of the commands that you type 'echoed' on the screen, but you will see the effects of those commands. Insert mode is used to add new text to the file and delete the text you just typed. The simplest way to get into insert mode is by typing 'i' when you are in command mode. This returns you to command mode and cancels any commands.