A sitemap is a file where you can list the web pages of your client's site to tell Google and other search engines about the organization of your site content. Search engine web crawlers like Googlebot read this file to more intelligently crawl your site.
Also, a sitemap can provide valuable metadata associated with the pages you list in that sitemap: Metadata is information about a webpage, such as when the page was last updated, how often the page is changed, and the importance of the page relative to other URLs in the site.
If your client's website’s pages are properly linked, web crawlers can usually discover most of the site. Even so, a sitemap can improve the crawling of the site.
