It's call "Text Fragments", and it was introduced to Chrome more than one year ago. https://github.com/WICG/scroll-to-text-fragment

I think it works in Chrome and Edge, but not in Firefox.

Thanks!

Indeed, it seems to be just those for now:

https://caniuse.com/url-scroll-to-text-fragment

In a Chrome browser on desktop, you can right click and "Copy Link to Highlighted Text". That's the context (hah, pun) where I know it from. It's really useful!