An administrative announcement.
Q: What's this "Federation thing?"
A: A bunch of communities, on different servers, sharing /some/ but not necessarily /all/ of their traffic. Or, in some cases, none. It depends.
The User Guide has a good section:
@arinbasu Understood. My documentation here is about what it /is/, not whether it is /ok/.
Helping people understand the system behaviour, such that they're not surprised by it.
Generalistic and moderated instance.