Firefox does several other things with AI too, and many of them locally, e.g. suggesting tab group names, suggesting other tabs to add to existing groups, auto-generating alt texts for images pasted into edited PDFs – each supported by a dedicated local model!

You can see which ones your Firefox installation has already fetched and their purpose on about:addons.

More about this here: https://support.mozilla.org/en-US/kb/on-device-models

On top of that, current mobile versions (and weirdly enough only mobile versions) can now also summarize articles using Apple Intelligence (where available) or Mozilla-hosted remote inference: https://blog.mozilla.org/en/firefox/shake-to-summarize/