A sitemap is a visual or text map of a website - an index of all web pages arranged in sections as they show up on the site. The sitemap is a single file and its presence may have a substantial effect on the popularity of your site, particularly when you have more content. It will permit your website visitors to browse the web pages and find what they need much faster, which will raise the possibility for them to return to the website or to show it to friends and colleagues. The sitemap is also needed for search engines to index your site content better, so that certain pages will be in the results for particular searches, which will most likely not happen without a sitemap even if you have the required content. This is especially valid when you update some web pages as the sitemap informs the search engines that they must crawl this website again to index the new content. Having a sitemap these days is essential rather than an optional attribute for any thriving site.