Sitemaps are basically a list of all the pages on your site. Search engine bots, like the Googlebot, crawl sites by following links from one page to another. If your site does not have many other links on the web and/or is relatively new, search engines could find your site difficult to discover. Especially in cases like these, and almost always otherwise, a Sitemap is a great insurance plan to let search engines learn more about your site.
You read right. Web 22.0. Not web, 3.0 or web 9.0 or even web 21.0 (all passé…google them) but Web 22.0. You heard it here first.