Text editing is basically 90% of command-line interfaces, and Emacs has its own Unix-like shell with Unix-like utilities (that work the same on every platform,

Text editing is basically 90% of command-line interfaces, and Emacs has its own Unix-like shell with Unix-like utilities (that work the same on every platform, even Windows), terminal emulator, file manager, a bunch of email clients (I stopped using any for a while, although I plan to try using mu4e over the holidays), add-ons for any kind of programming language and version control and build system, stuff like calendars and spreadsheets, a file system emulator that lets you transparently work with remote files over a bunch of different protocols (no need to try to set up NFS or whatever on Windows), and all this works the same on any OS and over a terminal connection. It is a great text UI for most computing tasks.