Well, it is standard SEO going on here. The more kw's you enter, the more likely you are to turn up in the results. The real key, is the same as on-the-page SEO - and that is to make sure you use those actual keywords during your video. I don't know the Youtube algo, but they do perform a voice-to-text translation on some vidoes (I don't know enough of yt to say when they do that). The moral, is to use those keywords in your video talk.

[techwiser.com...]

Interesting! Thanks Brett, also there are some hashtag / keywords tool websites and are they worth the money? They sure are charging a lot!

[edited by: not2easy at 3:12 am (utc) on Apr 16, 2019]
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KISS ... use keywords that actually match the content. Over-reach on keywords can have an adverse effect.

Yes, I would also agree that you need to use only keywords that actually match your content.
Check what keywords your target audience is interested in, and definitely use them. They help you get more reach

yes it matters. It tells to search engine what type of your content/Image/Video.

For YouTube, pay special attention to keywords in the title and the first paragraph of the description. Long descriptions are better than short ones. Try to make the description have some similarities with the script.

If you want to make your video searchable, then you should use the keywords and tags in your video content also. It is as important as for normal content. As well as the hashtags are also important to boost the searchability result.
Hashtags on Facebook and YouTube work in a similar way as they work for Twitter. You can add hashtags in your videos, that are more popular or they should be linked with your other videos.

Yes, I think it matters. Hashtags and keywords still useful for searches.

Yes, Hashtags are very important in social media sites because they work as a search tag. whenever some search for web development then in social media they popup the most relevant posts include the popular posts (which has more likes & shares)