Alternate Access Mapping in MOSS
Microsoft Office SharePoint Server 2007 (MOSS) supports Alternate Access Mapping (AAM) which allows the administrators to configure SharePoint so the users can access SharePoint sites using different URLs. The idea is to associate each Web application with a collection of mappings between internal and external URLs. For example, in certain situations, such as environments using reverse proxy or load balancing, the end user may type a different URL to access the site then the URL that is received by the Internet Information Services (IIS). In this situation, AAM will come handy and direct the user’s request to the proper URL.
You can also associate multiple internal URLs with a single public URL using one of 5 different authentication zones: Default, Intranet, Internet, Custom, and Extranet. Check out this TechNet articlefor more information on how to configure AAM in SharePoint.