Sitemaps and SEO
A sitemap is a file, or series of files, that help search engines crawl and index your website content. They also inform the search engines which of the pages on your site are the most important.
There are largely two types of sitemap, XML and HTML. XML sitemaps are not intended for human consumption and are specifically designed to inform the search engines about the URLs that exist on a website, how often the content is updated, and the relative importance of the pages. HTML sitemaps, on the other hand, are very much designed to be seen by users, and provide a 'birds eye view' of all the pages that the website owner wants you to see.
Are Sitemaps Important for SEO?
XML sitemaps are recognised by all the search engines that have any impact on your SEO and are a very powerful tool. With the various search consoles (Google, Bing etc) it's very easy to submit a single 'sitemap.xml' file, which shows the search engines all the pages that need to be indexed, all from a single file. This process can be streamlined even further by using an automated sitemap generator, which will run regularly and update all the URLs in your sitemap.xml file as and when they change.
What URLs Should be Included in a Sitemap?
There is some simple logic that can be applied here. Ask yourself two questions: 'What URLs do I want my users to find?' and 'What URLs provide value to my users?'. Once the list of URLs for both questions is exactly the same, that's the URLs that you should include in your sitemap - no more, no less. It's worth noting, however, that just because you may choose to omit certain URLs from your sitemap, it doesn't necessarily mean the search engines won't find and index the URLs. The search engines may pick up on pages via internal links - in which case, you can add 'nofollow' or 'noindex' tags to your internal links. Furthermore, you can also add specific 'nofollow' pages to your robots.txt file for pages you don't want the search engines to index when crawling your site.