The difference between focus keywords and meta keywords
The focus keyword field in Yoast SEO is specifically not the same as the meta keywords field in other plugins. By default, our plugin doesn’t give you a field to enter meta keywords, as meta keywords have been proven to be a waste of time. Joost has written an article on meta keywords that explains this. We’ve removed them from the plugin since version 6.3 of Yoast SEO.
The focus keyword (seen in the screenshot below) in the Yoast SEO plugin has a completely different purpose. This article on the focus keyword explains what the focus keyword is and what it does.