Users can make public collections to categorize resources. This is great for sorting a particular type of resource you're worried may not be found via search (or you just want to keep track of who has and hasn't been done in a series) or can't be filtered at all (such as my LoRA collecting resources for Pony that mimic a specific work or set of works since "style" filter is full of so many things for giving a particular mood, or copying a random internet artist). When you add a model or picture to a collection, the creator gets 2 buzz, which isn't a lot but it works on a separate daily cap to the images getting reaction one.
Of course, the huge and obvious problem is the complete and utter lack of discoverability for collections. As far as I'm aware there's no way to actually find them short of opening a user's profile and opening the tab and maybe finding a collection you are actually interested in. Logically you should be able to see what public collections a resource is in somehow and use that to find collections that list similar things, but this is seemingly absent from CivitAI for no apparent reason (I have a suggestion in the suggestion box on implementing such a thing. Go find "List public collections containing this model" and upvote it if you agree this should be done, and check my previous did you know article if you don't know about CivitAI's suggestion box)