The meta keywords tag is a tag which can be used to highlight keywords and keyword phrases which the page is targeting.
The code for a meta keyword tag looks like this
<meta name=”Keywords” content=”keyword phrase, another keyword, yep another, maybe one more “>
Many people spammed meta keyword tags and searchers typically never see the tag, so most search engines do not place much (if any) weight on it. Many SEO professionals no longer use meta keywords tags.