Every Web page has a homepage. It's the first page you see when you type in www.domainname.com and it is also called the "root" of your site. From your homepage you might have several links, "sub-pages" such as ABOUT US, CONTACT US, SERVICES. A flow chart of this setup would like like:

You can also have sub-pages of a sub-page. For instance, under SERVICES you might have several types of services, each represented by it's own page:

The layout structure above would consist of 7 pages.