[pbmonster]

As a very practical example: You take notes in org-mode, and as you do in many modern note-taking apps, you use copious links between notes.

But org-mode is inside Emacs, and Emacs is (can be) also your email client. So your notes can link to emails. Emacs is also your calendar. So your notes can link to events.

You can extend this to almost anything if you like Emacs enough. Your notes link to source code files (or your notes contain code, which can be executed from your notes). Emacs is also your git front end, so you could link to commits.

[eawgewag]

This is a great comment. My "Aha" moment with org-mode was when I started using it to track my TODOs on ongoing branch. I was able to link bookmarks to actual code from my org mode agenda, jump back and forth between my todo list and the actual code in my repo, add more, add context, etc.