This allows us to easily edit CSS on the front end without editing any of our files. I specifically remember reading that this feature allows us to write CSS that won't be overwritten by a theme update.
Now the time to update has come, and I'd like to absolutely confirm this. But I can't find any references to this button online.
What's this feature called? Is it on everyone's WordPress.org site, or is this some special feature of our theme or perhaps a plugin?