That happens on the server side and how the owner of the site configured it. Some sites would redirect you to the www subdomain. If you go to “example.com”, it (example.com) would redirect you to “www.example.com”. The www part is not assumed and not automatically added by your browser as is the case “with http”. And you can in fact have your server redirect connections to something other than the www subdomain or not redirect at all, you can also not have a www subdomain at all, but these are usually considered bad practices for public facing sites.