I wrote this article because I found there were a lot of "Is your "SEO Experts" stating that the meta tag keywords is important. Metatag keywords do not effect your search engine ranking in any way.
A metatag is placed in the <head> html tag of a web page and looks like this:
<meta name="keywords" content="yeoman,nick,web design" />
Google completely ignores the above meta tag in its core search. Matt Cutts has a great video explaining why Google does this.
Matt Cutts doesn't talk about why we would use the keywords metatag. One reason is for an internal search. Using the keywords metatag allows me to target certain articles for my search results, helping my users find better results. This creates a better user experience.