You may come across one you just might like. They change on a regular basis.
Edit for rule #2 - Trending communities show you new/active communities in the instance you are browsing from the instance’s home page. Example: My account lives on lemmy.world, but if I visit lemm.ee I will be able to see that instance’s newest and/or most active communities. Just another way to explore Lemmy and the fediverse from another noobie user learning things as I go along. :) Cheers!
From what I’ve seen they’re not so much trending as new.