Google Sitemap

A site map (or sitemap) is a list of pages of a web site accessible to crawlers or users. It can be either a document in any form used as a planning tool for Web design, or a Web page that lists the pages on a Web site, typically organized in hierarchical fashion.

Sitemaps make relationships between pages and other content components. It shows shape of information space in overview.

#  Sitemaps index file

To organise a bunch of sitemaps (for instance for each subdomain) you may want to consider creating a Sitemaps index file.