Vim

General

Vi or Vim (VI IMproved) is a visual text editor that can be run inside a shell. This has the advantage, that you can quickly write or edit text files in the shell, even over an ssh connection without needing a graphical user interface. Alternatively there is the option to edit files locally (on your desktop computer) in your favourite editor or IDE (e.g. Notepad++, VSCode, ...) and then transfer the files to the remote (super)computer. Visit the file transfer page for more information on that topic. As these tansfers can be a lot of effort, just to fix a missing ; or typo, Vi/Vim can come in handy, as they are available on practically every Unix system.

While it's usage is far from intuitive, a few basics are generally helpful. For a more complete coverage of this editor, why people use it and why you should probably do that too, please take a look at the vimtutor, the References or the internet in general. There are lots of great resources, presenting reasons for using Vi/Vim and giving detailed instructions for its effective usage.

Modes

In Vi/Vim there are two modes. Normal mode and Insert mode. You switch to normal mode with the ESC key and to insert mode by pressing i. Insert mode works more or less like you would expect a normal text editor to work with arrow keys for navigation, backspace for deletion and characters for text. More information about what normal mode is good for etc. can be found in the References or the internet.