Otherwise known as: the ability to click something and see all references related to that thing. Two examples might be: the ability to click on a tag inline to the text and see everything with that tag. Or the ability to click on a name of something and see all references to it, such as the name of a book. I can emulate this right now by creating a card with the name of that book and link to it. I can then click on that link and see all the backlinks, but it’s more steps to be able to see that context and it’s a different UI from looking at a search for cards. Technically I can also just do a search for the title in question, but having a UI element in a note that hints at there being more context that can be found is nice.
An example of what I’m talking about is the feature in the macOS software The Archive where you can put square brackets around any string and it turns it into a clickable link that will perform that search. I honestly feel like this is a really smart feature they put in that grants a lot of nice flexibility for finding/linking/etc. notes. (they use it exclusively for linking notes and have no auto-complete for other notes and whatnot so I think it’s overloaded a bit, but I do think it’s an extremely useful feature for knowledge management)
I apologize if this is rambly or unclear, please let me know if I can expand on anything more.