A sitemap is a type of document that is a general listing of web pages that can be indexed by search engines.
You can access your Hub's sitemap by appending 'sitemap_index.xml' to the end of your Hub's Home Page URL (example hub.domain.com/sitemap_index.xml)
With this URL you can use the Hub's Google Search Console integration and submit the sitemap for Google to reference in future indexing. This can help get your content crawled and indexed faster!
Things that are Good to Know
Currently the sitemap.xml file will reference content in the Hub's Home Stream, all Stream Level 2 Pages and only the latest 200 Items under each Stream.
The Hub's sitemap.xml file will only index content that has a status of 'SHOW' in your Hub. Hidden content will not be in the file.