How is an account's physical address determined?

I read a question about protecting his account and met the following words: "view the exact physical address where your account was logged into " how is that done? who are able to do that?

If you're referring to FunAdvice, we don't have that information nor could we give it to people. If you're referring to another site, then they might be doing something with an IP look up combined with an address look up of the org that the IP address maps to. However, that would be highly inaccurate most of the time.