How a video sitemap works
Like the image version, a video sitemap is an extension to the ordinary XML sitemap rather than a separate file. Under the URL of the page that shows the video you add a block describing it, and search engines expect the same core facts every time: a title, a description, a thumbnail image they can display, and either the address of the video file itself or the address of the player that runs it. Optional details such as duration, publication date and an expiry date can be added on top.
The reason all that is required is simple. A video is opaque to a crawler. It can fetch the file but it cannot watch it, so the surrounding information is what tells the engine what the video is, whether it is still available, and what picture to put next to it in results.
Why a video sitemap matters
Video results carry a thumbnail, and a thumbnail earns attention that a plain blue link does not. For a training provider, a clinic explaining a procedure, a trekking company showing a route or a product demonstration, that thumbnail is often the whole reason the click happens.
It matters most for video you host yourself or through a player that is awkward to crawl. A video published on YouTube is already discoverable on YouTube; the sitemap is about getting your own page recognised as the page that hosts it. Structured data using the video schema type does much the same job, and search engines accept either, so the choice is usually whichever your platform can produce reliably.
Where video sitemaps go wrong
The commonest fault is a lazy description. One sentence copied across every video entry tells the engine nothing, and it tells a searcher even less. Each video needs its own title and its own description, written for someone deciding whether to press play.
The second is a broken thumbnail. If the image address is wrong, blocked in robots.txt or too small to use, the entry cannot produce the result you wanted it to produce.
The third is listing video that has been taken down, moved to a new player, or made private. Dead entries linger in sitemaps for years and slowly turn a useful file into noise.
The fourth is hiding the video. If the player only appears behind a tab, a pop-up or a click, the engine may decide the page does not really show the video it claims to show. The video should be the visible point of the page.
What to do about it
Give each video its own page or a clear section on a page that is genuinely about it, with a real title, a written summary and, where the content justifies it, a transcript. That text is what makes the page findable for the questions the video answers.
Then let your platform generate the sitemap or the video structured data automatically rather than hand-writing entries that will rot. Check the thumbnail actually loads for an anonymous visitor, keep the entry only while the video is live, and review the video report in Search Console when something stops appearing. Doing that alongside the wider video and YouTube SEO work is what turns a library of clips into pages that get found.