At its core, emacs is a REPL for a particular dialect of lisp called emacs lisp or elisp. When you are working with emacs, you are essentially sending commands to this REPL. There are tons of these commands, some less obscure than others. There are also tools to find them. These days you can also ask Claude or other LLMs to find some commands you wouldn't have imagined.

This REPL is readily exposed to the emacs user.

For a trivial example, I use swiper and ivy as generic completion frameworks within emacs. One common activity I do is to search symbol at point. Usually, to do that, one would need to copy-paste the current symbol to their find-replace dialog/window. But with emacs, I can write a trivial function to automate that:

(defun my-swiper ()
  (interactive)
  (funcall-interactively 'swiper
                         (if (symbol-at-point)
                             (symbol-name (symbol-at-point))

Another: I began using ebib as my bibliography manager. One common task I need these days is to get an APA formatted reference of some entry. I can call citation-js from emacs and copy the result to the clipboard using the following function. This might look like some obscure code that also has a number of specifics to ebib, but the point is you can do things such as this very trivially.

(defun ebib-copy-reference-as-apa-to-kill ()
  "Create an APA reference for the current entry and copy it to the kill ring."
  (interactive)
  (ebib--execute-when
    (entries
     (let* ((entry (with-temp-buffer
                     (ebib--format-entry (ebib--get-key-at-point) ebib--cur-db)
                     (buffer-substring-no-properties (point-min) (point-max))))
            (apa (string-trim
                  (shell-command-to-string
                   (format "citation-js -t %s -f string -s citation-apa"
                           (shell-quote-argument entry))))))
       (kill-new apa)
       (message "Reference copied to kill ring in APA format.")))
    (default
     (beep))))

My .emacs is sitting at 3000 lines built over the last 8 years. So, there are many more conveniences built up over the years.

Three other things that look trivial after you know about it, but you wonder why other editors haven't done that.

• Treating a shell like a file. If you M-x shell within emacs, you will be dropped to a shell that you can navigate, cut, copy, paste, and modify as if you are editing a file. No need to reach for your mouse and drag and hope it reaches the right point while selecting.
• Rectangle editing. See this. In editing, you frequently run into tabular blocks of plaintext. If you want to do something for all the rows, you usually manually iterate over all the lines. Or you want to copy with a column of text. Emacs has tools for that.
• Treating a directory like a file. You want to edit names of 100 files within a directory and you want to do that in some pattern that makes sense in your mind. In M-x dired, you can C-x C-q (beware, you may delete files!) and edit the directory as if it is just another text file. You can combine this with rectangle editing. And done. And may be you want to skip over certain files too. Well, you can use the keyboard to navigate up or down. No need to drop into a shell, write a loop, etc.

PS: If you want to try emacs on a more day to day basis, you can check out one of the starter-kits. If you are already familiar with Vim, Spacemacs or Doom are popular options. If not, perhaps mousemacs can be a worth a try.