In plain text you can see on the screen almost the same what is stored in the file, plus minimal set of control characters like a new line and tabulator. That makes plain text not so fancy, but you can read it on almost any computer in the world.
Linux configuration files in /etc directory are mostly plain text, so if you want to tweak your system to fit your needs you will need some plain text editor.
Especially if you want to change the content of files (edit it) that are important for your operating system you may want to depend on as few programs as possible while you are editing. Therefore you might want to start a text editor that can be used via a Command Line Interface (CLI or one meaning of console) and does not depend on a Graphical User Interface (GUI).
Editors For Use from Command Line Interface (console)
- vi is part of UNIX
- Vim is a clone of vi with additional features and mostly used in Linux systems by commands with "vi".
- GNU nano (or nano) is a minimalistic editor and almost an exact clone for Linux systems of the older pico.
- mcedit is a pretty comfortable editor, and part of the Midnight Commander file manager.
- Emacs in another text editor.