The meta keywords tag is a HTML tag that indicates the main keywords of the page to search engines. It was once used a lot by SEO experts (about a decade ago). Back then, it was just enough to place the keywords of the page in this tag to rank for them.
The abusive use of that tag pushed the need for a better way to rank websites. This is why search engines are no longer using it. Bing has even stated in the past that it uses the keyword meta tag as a spam signal.
In SEO, this <keyword> tag is no longer useful, so avoid inserting it in the source code.