Emacs configures its fonts through fontsets. 'nough said?
Emacs comes with a sample file called
HELLO that contains the word “hello” in some common scripts. You can display it with
C-h h (press Ctrl+H then H). Even those are often not all provided by the same font. You can run
M-x describe-fontset (Alt+X
describe-fontset Enter) to see what fonts are used for what code points. If you work with less common scripts, you may need to modify the default fontset in your configuration file. The details are in the Emacs Lisp manual; if you can't figure it out, there's a whole Stack Exchange site where you can ask for help¹.
You may want to define multiple fontsets, e.g. one with maximum breadth for writing linguistics texts and one that's ASCII-only, fixed-width and taking up less screen real estate for programming. If you do this, bind the command
mouse-set-font to a keystroke or to a mouse button combination, to make the switch easier.
For programming, Emacs has support for syntax highlighting, automatic indentation, build automation, identifier completion, documentation lookup and other nice features, some of it built in, some more advanced stuff through third-party packages.
Emacs is free and open source. There are official Windows binaries as well as several third-party distributions which may have nicer installers or useful bundled tools.
¹ Disclosure notice: I'm a moderator there.