Sitemaps are list of your website's urls or web pages, by submitting these to search engines you provide them an easier way to crawl your website.
One major advantage of submitting sitemaps is that you call the attention of search engines that some changes, additions or deletions have been made to your website. This will prompt them to crawl your website the soonest possible time, although we cannot tell how long it will take for them to visit your site.
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Submitting Sitemaps to Google