Seo Master present to you: 
To know XML site map first we need to know about sitemap. Sitemap works  as a road map of any website. Using the road map we can easily find our  destination just like that using the sitemap of any website we can esily  find their web page's imformation. Just like that an XML sitemap works  for search engines spider.
XML sitemaps are created particularly for the search engines spider. All  of the most well-known search engines including Google, Yahoo and Bing  operate XML sitemaps as part of their practice for indexing the web  pages of a website. A good XML sitemap will inform the search engine  what pages are in your website, how frequently those pages are updated,  and when they were previous modified. This way, the search engines know  which web pages to revisit more frequently, and are possible to do a  superior job of indexing them.
Following codes are example of what a simple XML Sitemap might look like:
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
   <url>
      <loc>http://www.example.com/</loc>
      <lastmod>2005-01-01</lastmod>
      <changefreq>monthly</changefreq>
      <priority>0.8</priority>
   </url>
   <url>
      <loc>http://www.example.com/catalog?item=12&desc=vacation_hawaii</loc>
      <changefreq>weekly</changefreq>
   </url>
   <url>
      <loc>http://www.example.com/catalog?item=73&desc=vacation_new_zealand</loc>
      <lastmod>2004-12-23</lastmod>
      <changefreq>weekly</changefreq>
   </url>
   <url>
      <loc>http://www.example.com/catalog?item=83&desc=vacation_usa</loc>
      <lastmod>2004-11-23</lastmod>
   </url>
</urlset>
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