Should I use them?
There has been a great deal of debate about the benefits of the 'keywords' <meta> tag over the past few years but the truth is that it is no longer supported by the major search engines.
What do the search engines say about Meta Keywords?
Google officially dropped it in 2009, stating that they no longer give the meta tag any value when ranking pages.
Yahoo and Bing have the same policy. However, some people maintain that Bing does read the meta keywords tag in order to determine whether your site or pages on your site, should be considered as spam. So, at least in Bing's case, getting it wrong can be much worse than not using it at all.
You will notice that one field that has recently disappeared from your SEO Tools is SEO Keywords. Previously, there was an option to add a list of comma-separated keywords that you wanted to rank highly. Now, Google is no longer giving meta tags/keywords any value when ranking pages and may in fact penalize websites for using them. Therefore we have now removed this option from the SEO Tools section of your website CMS.
This tool will tell you where this keyword exists on the website and it can suggest where you should add that keyword (e.g. Title, description). It is there to help you when you have a strategy for a certain page that you decided on.