It can federate with lemmy, essentially just being another type of node in the same web of individual websites.
Some of those sites are hosted with lemmy, some are hosted with piefed, some are hosted with mbin.
Each of those (lemmy, piefed, mbin) is a piece of software that can run as a “server” for a social media site, and can use the activitypub protocol to talk to other sites that are federated together making the contents of other sites visible. They can federate regardless of whether the software powering the site is the same or not.
wjs018@piefed.social 3 days ago
Well, it can federate with lemmy instances and there are way, way more lemmy users/communities than there are piefed user/communities. If you want to see the local communities on a piefed instances, it would be at
/communities/local. This is the page for piefed.social.