A Sitemap is an XML file that lists the URLs for a site.
It allows webmasters to include additional information about each URL: when it was last updated, how often it changes, and how important it is in relation to other URLs on the site.
This allows search engines to crawl the site more intelligently.
Importance of sitemap:
XML Sitemaps are critical for search engine optimization due to the fact they make it simpler for Google to locate your website's pages—that is important due to the fact Google ranks internet PAGES, not simply websites.
There isn't any downside to having an XML Sitemap and having you can actually improve your search engine marketing, so we distinctly advise them.