An XML sitemap is important for SEO because it helps search engines like Google find and understand all the pages on your website. Think of it like a map that shows search engines where everything is and how often it gets updated. This is really helpful if your site is new, big, or has pages that are hard to find through regular links. By using a sitemap, you make it easier for search engines to crawl your site, which can help your pages show up in search results more quickly.