What the Internet should have been
The TCP/IP protocol, on which the Internet was built, was designed so that each connected device can be both client and server. It was intended to result in a distributed structure rather similar to this:
What the Internet has become
But in practice, the Internet has become a service space: we have customers (u) on one side, and servers (s) on the other. This has resulted in a “multi-star” structure: in the world, we have billions of users connected on a handful of services that everyone knows (including GAFAM). In this structure, no two users are directly connected to each other, they all have to go through a service. Some people rightly speak of Minitel 2.0:
Internet service providers
And we must also mention at this point the internet service providers (isp) which have a central role: they are the link between users and services.