Metaphors on your Website
Using metaphors means to use objects from the real world to represent either a whole web site or design elements in your community.
This helps the users to understand more quickly how to use the site, or to more quickly understand how it is supposed to function.
So when users get to your site they will automatically be trained in how to use your site, simply because they understand the object, your site is designed to emulate.
For example: The bottom-most layer on a Windows interface is called the desktop, which a metaphor meaning that this bottom-most layer is like the literal top of an office desk:
You can place things like files and folders on it, you can rearrange or you can order those items upon it.