The sources are urls to the cited page (e.g. stackoverflow.com, pkg.go.dev). In the side-bar next to the answer is a more standard search-result style link list with pulled quotes from the pages (like a Google search).

I didn't click every single link (as I mentioned, the citations are copious) but the few I did follow went to relevant articles. I just went back and randomly clicked several more and they all went to pages that exist and mostly relate to the content of the answer. The inline citations seem a bit more on-topic compared to the side bar which does seem more like the links were lifted directly from a search engine.

To be fair there are some lower-quality blog-spammy kinda stuff - more or less the same kind of thing you would get out of Google. But compared to GPT-4, which provides no sources whatsoever, it is an advantage IMO.