An XML sitemap is a list of all the URLs that make up your website. It is structured in a way to make it easier for search engines to recognize and index the various pages of your website. If you have a WordPress site or a website built with a CMS, the XML sitemap is automatically built with a plugin or module. You don’t actually have to do anything except submit the sitemap to Google Webmasters Tools.
If you have a website with no CMS and edit/add pages with HTML, you will need to create a XML sitemap manually. This is very easy, just go to the website https://www.xml-sitemaps.com/ and enter your URL. The instructions for downloading and saving the sitemap are right on the front page of the site!