lemmy.ml, beehaw.org would most likely host generic versions of those. But as the network grows there may be more and more specific categories people may be interested in, that don’t have to or shouldn’t be on one server.

E.g. technology. lemmy.ca could feature Canadian specific tech. Feddit.de would have most articles in German. A FOSS-oriented instance would have most articles to do with open source

The server you sign up with mainly controls what you see by default in your home. If you want to see less politics and more tech related stuff then you would sign up on a tech-focused instance. Or if you don’t like the rules or the moderator of your current server, then you can create an account on another server. You need to abide by the rules of the server you post to if you post outside your home server.