For a web site to be made available on the Internet, it has to be hosted on a web server. This is where web hosting comes in. It's just like renting property. There are plenty of companies that will rent you space on a web server. The wide range of services start from free hosting to buying a server for your sole use. You could spend thousands of dollars a year on web hosting alone.
Choosing a host is not an easy task. There are so many features, services and options to consider. The most important factor is making sure that the host you choose will provide everything that you need. Read through Web Hosting Explained and then use Web Host Directory to select the right host for you.