If I understand it correctly it’s basically community to community federation, so when you subscribe to a community it also pushes other community posts it follows to your subscribed feed. Those posts would still show up as those other communities. A community becomes not just a place to post, but also as a curator that vouches for other communities as well. You could even potentially have a curate only community like a lemmy best community list to get newbies started, or category level communities.
Like many shitty things in the world it appears to be incited by Russians https://www.google.com/amp/s/amp.theguardian.com/world/2023/jan/27/burning-of-quran-in-stockholm-funded-by-journalist-with-kremlin-ties-sweden-nato-russia