A sitemap is a visual or text map of a site - a list of all pages grouped in sections as they appear on the website. The sitemap is a single file and its presence may have a significant influence on the popularity of your site, especially when you have more content. It will allow your visitors to go through the webpages and find what they need quicker, that will raise the possibility for them to come back to the website or to show it to colleagues and friends. The sitemap is also required for search engines to index your content better, so some pages will be in the results for certain searches, which will most likely not happen without having a sitemap even when you have the needed content. This is especially valid when you update some web pages as the sitemap tells the search engines that they must crawl this website again in order to index the latest content. Having a sitemap nowadays is fundamental rather than an optional attribute for any profitable Internet site.