A keyword is the word you type into Google when you’re looking for something. For example, I want to show up on the results page if anyone types in “WordPress Support Packages”. So WordPress support packages are my keywords. In this case, it is a long-tail keyword, which means it is a phrase or description. The keyword (singular) would be WordPress.
Long tail keywords are really valuable because it is likely I’ll never show up anywhere near the homepage for WordPress. But if I work really hard, I could for WordPress Support Packages.