Meta keys are intended to describe the purpose of the site to google boots.
Example My Site:

Meta Keywords: How a Meta Keyword Plays a Small but Important Role in Search Engine Marketing
Meta Keywords are a specific type of meta tag that appear in the HTML code of a Web page and help tell search engines what the topic of the page is. Meta keywords are distinguished from regular keywords because they appear “behind the scenes,” in the source code of your page, rather than on the live, visible page itself

Meta Keywords is the meta tag which appears in onpage optimization of web page to crawl search engine what the topic of the page is

A few years ago you could put in keywords into your meta tags and search engines would could these towards your SEO ranking. This is no longer valid though.

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With help of keywords search engines and users can easily understand website. The meta keyword is a HTML tag where we can put the Title and descriptions etc for a page. This is basically help search engines to understand what is page about and present your website according to your titles and descriptions.

Meta Keywords are a specific type of meta tag that appear in the HTML code of a Web page and help tell search engines what the topic of the page is.

Meta Keywords are a specific type of meta tag that appear in the HTML code of a Web page and help tell search engines what the topic of the page is. Meta keywords are distinguished from regular keywords because they appear “behind the scenes,” in the source code of your page, rather than on the live, visible page itself.