Helping Google with site maps
A site map is just that—a map. It outlines the structure of your website and includes pertinent information such as last updated and update frequencies. Just suppose you add an important product to the bottom of a big subcategory. In all likelihood, Google must crawl through your entire site to find it and add it to the search results.
With site maps, Google can be aware of this page, any others, and any modifications. Google can then specifically crawl the new or updated pages. This is better for you and easier for Google.
