When it indexes a video, Google gets to know about the file. It uses the information on the file and on the page to make sense of the meaning - and thus the related question. This does not mean, incidentally, that Google will create a video rich-snippets in search results.
An indexed video may be eligible for an autoplay preview in which searchers can view a short clip while hovering over it, such as on YouTube. So far, though, those previews seem to work primarily for actual YouTube pages in search results, but reports may indicate Google's intention to expand the feature.
Google lists several possible reasons why a video is not indexed. The most common are faulty embed codes. This is typical for older sites that use non-YouTube embeds or plugins. In most cases the fix is to update the code and validate the page in Search Console.
There are two possible solutions for a page with a video that isn't in the "Video pages" report: stop. The report is new and will eventually include more pages. In addition, new pages take time to display. Confirm that the host page is indexed using Search Console's "URL Inspection Tool". For an indexed host page, make sure your video is visible and playable on that page.