The internet is interconnected routers, all assigned numbers.
In some countries the numbers are assigned by the Govt as a service. Public internet service provider.
In some countries the numbers are assigned by private internet service provider.
They also can manage things like flow speed and such.
Scott Forman universities and us military handled it for decades. But they were done with the experiment by the early 1990s.So seeing a sort of free market opportunity (not really at all) congress and the Clinton administration auctioned the trunks to four companies. Att, mci and I forgot who now.They in turn rented access to regional and local isps and that’s how it’s been operating ever since for the usa.
But there are trunks in other countries that handle it differently.
cell phones are just walkie talkies amplified by towers hooked into the internet by wires.
For that you rent the air space bandwidth as well as the internet wire bandwidth as a user.
websites are usually rented hard drive space on someone else’s computer with a better uplink internet connection than you (usually) dedicated to serving webpages.
The numbers are turned into names by a domain name server (DNS), many are public some private. There’s special ones that give you access to “hidden web” stuff too.
Most use google 8 8 8 8 or level3 4 2 2 1 or whatever their isp provides.