Google introduced the Sitemaps protocol so web developers can publish lists of links from across their sites. The basic premise is that some sites have a large number of dynamic pages that are only available through the use of forms and user entries. The Sitemap files contain URLs to these pages so that web crawlers can find them. Bing, Google, Yahoo and Ask now jointly support the Sitemaps protocol.
Since the major search engines use the same protocol, having a Sitemap lets them have the updated page information. Sitemaps do not guarantee all links will be crawled, and being crawled does not guarantee indexing. Google Webmaster Tools allow a website owner to upload a sitemap that Google will crawl, or they can accomplish the same thing with the robots.txt file.
XML Sitemaps have replaced the older method of “submitting to search engines” by filling out a form on the search engine’s submission page. Now web developers submit a Sitemap directly or wait for search engines to find it. Regularly submitting an updated sitemap when new pages are published may allow search engines to find and index those pages more quickly than it would by finding the pages on its own.
It’s recommended to use a sitemap for better website experience.
If you’d like to create your sitemap you can try out different free ones online. Here is one below.