When you tell the browser to go to that address, what you are asking the browser to do is to communicate with a Web Server running on a computer somewhere on the Internet. Every computer on the Internet has a unique name like this. The infrastructure of the Internet can route the request thousands of miles in a split second, finding the right computer and contacting the Web Server. Web files have the extension .html or .htm. If it finds the file, it starts sending the file to the browser.
All networks do is transfer data.
But browsers know what to do with HTML data. When your browser starts receiving the file, rather than just saving it somewhere on your computer, it starts reading it. Every month browsers grow more sophisticated. Today browsers function like virtual computers. Web Developers can put software code into a web file, and the browser will run these tiny applications to add dazzle to their pages and in some cases add functionality.