Have a website being indexed by Google is important to your website and its online success. One of the ways this is achieved is by having a sitemap installed. A sitemap helps Google crawl and index all the pages contained within a website.
A site map also provides a structured and organized navigational hierarchy of links and pages on a website. This helps users and Google to navigate and crawl a website with ease as search engines rely on links to find the main pages on a website.
There are a lot of extensions and plugins that can automate this process in WordPress and Joomla such as Google XML sitemaps or Xmaps.
In conclusion, one can think of a sitemap as a map for users and search engines to easily navigate around your website.
To find out more detail about sitemaps view the video below.