Keyword meta tags were meta tags added on to the page, to indicate the page’s main keywords. It started in 1995 when the world of the web was more or less innocent. Google, Yahoo or Bing does not consider this tag as of now.
Keyword meta tags
The meta tag is an element which is visible to crawlers but not to visitors. A meta keyword tag will look something like below.
<meta name="keywords" content="cars, used cars, spare parts, cars for sale, best car in the world">
But it does not work with google anymore Watch below video
Yahoo in 2009 followed by Bing in 2014 has stopped using meta keyword for indexing pages.
Focus keyword is keyword or phrase, for which you wish your page to be ranked for. The presence of the word or phrase in the page content will help you to achieve better ranking in SEO. Note that, there is no need as of now to mention in as a meta element.
There is always a temptation to use single focus keyword on different articles over an over, which is not recommended (as it might result in your own page competing with each other)
Use this link for better keyword search