Unlike the Index Page, most pages within a website tend to have a similar layout or design. This is usually to make it easier to navigate throughout the site.
Most page layouts include a Header Graphic at the top of the page, accompanied by the main navigation bar, a sidebar, and a footer. These elements tend to be the constants, and are usually placed in the same spots wherever you might navigate within the site. The only element that changes is usually the content of the page itself.
Some websites can have dozens, if not hundreds of individual web pages, however. To conveniently make changes to all of these pages, this is where the Master Template comes in.
The Master Template saves all of the common settings and layout of pages other than the Index Page. This means that if you create a new page, you won't have to create the page from scratch, and you can focus on adding the actual content to that page. This also means that once you make layout or design changes to the Master Template, these changes will also be applied to all other pages on your site that use this template (which is the default).
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