The Fediverse is a network of thousands of independent social media servers of many different kinds.
The most popular kind is Mastodon, but it wasn't the first and isn't the only one. Some of the accounts you interact with are on other server types, e.g. @Iancylkowski is on Pixelfed and @theatticdwellers is on PeerTube. There are many Fediverse server types:
Whichever type you're signed up on, they connect together to form a social network called the Fediverse.
@feditips Unfortunately I had to discover that it does not work that way. The results I get an a hashtag serach differ dramatically depending on how big the instance is that I search from. To test that I did setup my own instance and tested from that and from accounts on smaller and bigger instances. I get A LOT more results on a big instance than on smaller ones. IMHO that defies the purpose of the #Fediverse and is a major problem ...
Less connected servers can mitigate this by using relays, especially the newer topic-based relays:
https://fedi.tips/using-relays-to-quickly-expand-a-servers-view-of-the-fediverse/
I don't think this is linked to server types though, federation visibility issues would be the same even if every server was the same type.
@feditips subscribing to relay.fedi.buzz topics and sites works great, but the other relays I subscribed are still showing "pending" after eight hours. That does not seem to be a solution.