Many websites have pages that show sitemaps — a hierarchal list of pages within a site. For our purposes, a sitemap is an XML file that resides on your server and is read by Google and other search engines to learn about your site.
If you've ever worked with Google Webmaster Tools (https://www.google.com/webmasters/), you're familiar with the concept of providing a sitemap URL to Google. By doing so, Google can become fully aware of the pages and products within your Magento store without having to figure it out themselves. Sitemaps are an important component of your Search Engine Optimization (SEO) efforts.
Magento 2 has a built-in sitemap functionality that you can configure to generate sitemaps for each store view within your installation.
To create a sitemap for a store view, go to Marketing | Site Map in the Magento 2 backend. Click on Add Sitemap.
For our first sitemap, we'll create one for our furniture store view. We only have the one English language view for that website.
sitemap.xml. However, if you use the same file name for each store, you would not have unique sitemaps for each store view.The fields mentioned above can be visualized in the following screenshot:

When Magento returns you to your list of sitemaps, you can click on the listed URL to view the actual XML file. The first part of your sitemap file may look like this:
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:content="http://www.google.com/schemas/sitemap-content/1.0"xmlns:image="http://www.google.com/schemas/sitemap-image/1.1"> <url> <loc>http://acmefurniture.novusweb.com/sofas.html</loc> <lastmod>2015-12-06T17:24:17+00:00</lastmod> <changefreq>daily</changefreq> <priority>0.5</priority> </url> <url> <loc>http://acmefurniture.novusweb.com/sofas/couch.html</loc> <lastmod>2015-12-30T23:09:56+00:00</lastmod> <changefreq>daily</changefreq> <priority>1.0</priority> <image:image> <image:loc> http://acmefurniture.novusweb.com/pub/media/catalog/product/s/a/sample-couch-red_2.jpg </image:loc> <image:title>Couch</image:title> </image:image> <PageMap xmlns="http://www.google.com/schemas/sitemap-pagemap/1.0"> <DataObject type="thumbnail"> <Attribute name="name" value="Couch"/> <Attribute name="src" value="http://acmefurniture.novusweb.com/pub/media/catalog/product/s/a/sample-couch-red_2.jpg"/> </DataObject> </PageMap> </url>
This XML code is parsed by search engines to determine all the products and content of your site. You can control the frequency and importance of various sitemap elements under Stores | Configuration | Catalog | XML Sitemap.
The discussion of these elements is beyond the scope of this book. For a good explanation of indexing sitemaps, go to https://support.google.com/webmasters/answer/156184.