This is the presence of your site's pages in the Google Catalog.

Be careful, being indexed by Google does not mean being well positioned in the search results: it is simply the basis of SEO work. Can not be visible if you do not appear in the engine index!

Ensuring the proper indexing of a site is to ensure that nothing prevents Google or Bing robots from visiting and storing the site in their respective indexes. It is also to ensure that useless pages for the user are not found in the search results.