Sitemap as the name suggests is a map of the website that has a list of all the pages and sections of that website. Think it of as an index page of a book or a map of a town. If in a book, you want to get straight to a certain section, you would open the index and locate the topic and then open the corresponding page. The sitemap serves the same purpose as well – it shows to the website visitors all the sections the website has and allows them to click on a section name to directly get to that page. It also gives an insight to the website users of all the sections and pages the website has. An ecommerce website development company may suggest that it is useful for only a certain kind of websites like big ecommerce website, but the fact is that it is helpful for all kinds of websites (of course except for one to five page websites).
As per wikipedia’s sitemap definition: it is a planning tool used to decide or plan or list the hierarchy of a website’s pages. So if we are building an ecommerce website, we would first decide the pages and sub pages the website will have. For example the main categories, sub categories and possible sub-sub categories etc., We would then plan the design and structure of the website accordingly. So this is the first use of the sitemap. Then after the site is ready it is added to the site as an index page to help the visitors.
Its a helpful tool that makes the website user friendly and also search engine friendly -as search engines crawlers get one page that has all the links to the site and thus can index them all.
There are two types of sitemaps HTML and XML. HTML sitemap is the page that has links to all the pages of the website. Like the sitemap of this website on which you are reading this blog. A sitemap.xml file is a search engine crawler friendly file that webmaster adds only for search engines in order to give them a list of the pages that the website has.
Whether html or xml sitemaps, it is important for them to be updated all the time.