A sitemap is a visual or text map of a site - a list of all web pages grouped in sections as they show up on the website. The sitemap is a single file and its presence can have a considerable influence on the popularity of your website, particularly when you have a lot of content. It will permit your site visitors to browse through the webpages and find what they need way quicker, that will increase the chance for them to return to the site or to show it to colleagues and friends. The sitemap is also essential for search engines like google to index your site content better, so that certain pages will appear in the results for specific searches, which will most likely not happen without a sitemap even when you have the desired website content. This is especially valid in case you update some pages since the sitemap informs the search engines that they have to crawl the website again in order to index the new content. Having a sitemap these days is fundamental rather than an optional feature for any thriving website.