Google sitemap is a tool to help Google search engine to crawl your web site. It is XML structured file like this:
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd" xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<url>
<loc>http://www.googlesitemap.net/</loc>
<lastmod>2011-01-26T14:44:00+00:00</lastmod>
<changefreq>daily</changefreq>
<priority>1.0</priority>
</url>
<url>
<loc>http://www.googlesitemap.net/2010/10/11/what-is-google-sitemap/</loc>
<lastmod>2011-01-26T14:44:00+00:00</lastmod>
<changefreq>monthly</changefreq>
<priority>0.2</priority>
</url>
<url>
<loc>http://www.googlesitemap.net/privacy-policy/</loc>
<lastmod>2011-01-26T14:25:13+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.6</priority>
</url>
<url>
<loc>http://www.googlesitemap.net/contact/</loc>
<lastmod>2011-01-26T14:00:40+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.6</priority>
</url>
<url>
<loc>http://www.googlesitemap.net/about/</loc>
<lastmod>2010-10-11T12:59:48+00:00</lastmod>
<changefreq>weekly</changefreq>
<priority>0.6</priority>
</url>
</urlset>
And if you open this xml sitemap in a browser the output will be like this:
