The main ideas to understand are that:
The World Wide Web is nothing more than a large number of interconnected client and server computers
Websites are accessed by client computers via the web browser
Each website has a unique addresse determined by its domain name
Website files are stored on server computers that wait for requests from client computers
We have deliberately not gone into great technical detail here. Nevertheless, this article should give you a basic understanding of how the World Wide Web works and what's required to have a website.