The “submit sitemaps” tool is used to immediately notify search engines that the sitemap file has been updated and to request that they crawl the links contained within. Otherwise, you may have to wait weeks for them to discover new changes to your sitemaps on their own.
In fact, this tool works so quickly that you can see Google’s bots fetching the latest version of the sitemap in your server logs within seconds of using it.
If you introduce new content to your website, you may either wait till search engines discover it, or you can help them out by providing a sitemap.
You can learn more about this topic from Google or Bing.
There are multiple ways how you can notify search engines about new content.
This tool pings Google and Bing with the URL of your sitemap. It will also store this URL in a cookie, so you can easily resubmit it in the future.
I hope you enjoy using the tool, cheers!