It is a sprawling growing network of networks that span the world. The Internet has everything attached but the kitchen sink. Everybody that uses the Internet pays for a piece of it. The ISP does the same with the provider for his access to an Internet Gateway who in turn pays his share to a backbone provider. In between the links are thousands of companies providing equipment such as PCs, Servers, Routers, etc.
Advertisers pay for much of the free stuff available.
It seems that the Internet suddenly appeared out of nowhere. It came on like gangbusters in the '90s because companies called ISPs saw a market for affordable access to Internet. Before that, users were mostly institutions. Even earlier, users were restricted to institutions doing research for the government. In New Bern, the Internet began in 1994 when Coastalnet started with 3 employees and offered access to 91 subscribers.