That means that the entire screen is used while editing a file. In order for vi to work correctly, you must be using terminal emulation that supports moving around the screen. VT100 and VT220 are the most common emulations that support screen editing. If no filename is specified, vi opens a new document. The input mode is used while inserting text into the file.
Some commands are available in input mode, but most are only available in command mode.
Command mode is used for moving around the file, deleting or inserting blocks of text, and saving the file. In addition, command mode can be used to execute shell commands such as ls and more . ESC can also be used within command mode to cancel a command that has been partially entered. When entering a command in command mode, entering a number before the command will cause the command to repeat that number of times. As stated previously, one of the greatest strengths of vi is its ability to move around within a text file using a minimum of keystrokes.