Every website used to be like “www.example.com”. Now I rarely encounter this “www.”. Why did it even exist and where has it gone? I also used to run into websites with legitimate domains, but “ww1.” instead of “www.”, these were probably phishing sites, but how did this actually work on top of legitimate domains?
Those are schemes and they are not new, there are many others as well. Some you may see in a browser are http, mailto, file. Others that you won’t typically see in browsers include ldap(s), imap, jdbc, odbc, etc. https://en.wikipedia.org/wiki/List_of_URI_schemes