What whis means is that it is possible to open arbitrary applications on your system through a bookmarklet while sending data extracted and preprocessed from the current page by custom JavaScript to that application with the click of a button.

How to create a new URL scheme (such as org-protocol://)

what is really neat here is that with a .desktop file and a bookmarklet, you can send Web data directly from the browser to any local application!

How do we get to a world where our GUIs are as powerful and extensible as our CLIs? When I click Open in Emacs on my bookmark toolbar, and Emacs opens to the code I had open in my browser, I feel like I get a little glimpse of that world that could be.