Keywords are great allies to increase your chances to be suggested to a potential audience that would like to watch your content. Using searchable keywords and keywords your peers/competitors are using, is useful to have your content exposed to relevant audience that don't know you yet.
The strongest place to put on your keywords will be your title, after your description to make your SEO stronger, and last, your tags.
Some creators believe that there is no need to care about your tags, but they can be super helpful to tell YouTube which new audiences may appreciate your content. Use similar tags your peers are using, and misspelled words that people can search, such as “a lot” or “a lot”.
If you don't effectively use keywords to describe your video, YouTube will be forced to rely on extrapolating from your existing audience to find new viewers. This can be particularly limiting when introducing new topics on your channel that you don't have a history with. i.e. a new game, a new challenge or trend, current events, etc.