In fact, Joomla is a perfect example of how a client-server system can work to provide many different types of services and serve them up to a client as one "package" such as a web page. If a client's browser requests information such as images, text and other media, the server will find that information and send it back to the client's browser.
If you go to a Joomla site, which you have right now, you are the client requesting information and services through your web browser. The beauty of Joomla is that you don't need to know anything at all about any of this in order to build amazing websites and present your ideas to the world.
To see how easy it is to put Joomla to work, visit our free Joomla tutorial course - The Basics.