If I have an account on Mastodon.Social, and another account on PieFed.Social are they technically on the same instance, since they're both on .Social?
The cost of a (word).com domain can be tens of thousands of dollars if nobody owns it to millions of dollars if someone does. The cost of a (word).social domain is like $10.
Yup, this is why most Fediverse platforms are hosted on domains with TLDs that seem unusual (.social, .io, .ml, .xyz, .land, etc). Since most of these projects are funded by donations (if funded, at all), the domain is an excellent place to cut costs on a project like this.
Mastodon.social is the address to that specific Mastodon instance.
Take a look at this site for more info.
why not make everything (instance).com?
I’m not exactly sure what you mean by that? Are you suggesting everyone to use a ().com? If so, because they are rarely available and if they are, quite expensive.
You can register a second level domain (e.g. "google", "lemmy”, "cnn") with a specific TLD, resulting in a domain name (e.g. "google.com", "lemmy.social", "cnn.com")
The devout Christians currently going through a crisis on whether to go with "Jesus is in all of us, thus yes" or "Our boy J don't want none o' that nastiness".