Still very new to lemmy, but how one would choose which "instance" to register on? I would expect this post or similar one would kind of advertise to "register here"? And what does it lead to, really? Do I login with same account on other website? Based on some other posts across this lemmy thing, instances write down logs of users?

There is sure a lot of questions, and I just think it would be nice both for this instance and general community to see some basic explanations around whole thing as close as newcomer can see it.