What is sitemap for apps?
An App Content Sitemap allows you to manually submit an index of your pages to Google.
Why is a sitemap important?
A sitemap lists a website's most important pages, thus, making sure search engines can find and crawl them. Sitemaps also help in understanding your website structure, making it easier to navigate your website. You would want Google or any other search engine to crawl every page of your website, correct?