Anonymity online

The IP address doesnt tell much about a particular person. Just by looking at the ip address say 123.123.123.123 wont say much other than what service provider your with and country (possibly region im not sure) your in.

However, reputable websites can get bring in cops (or similar authority) for particular reasons. For example say you rip somebody off on Ebay and its cost like a million dollars, the police can trace the IP back to YOU, and all the details you gave your ISP (Internet service provider) can be given to the cops.

All internet activity that you do goes through your ISP and if authority figure requests info (FBI for instance) then they can trace whatever actions you obviously did bad back to YOU.

However if some random dude on the internet wants to see who you are, they cant, they can only say hey you live in OZ or America or whatever.