Keywords should be thought of as phrases rather than single words. They are the words people use to find your site on the Internet. These words are typed into a search engine which then brings up a list of websites related to that phrase.
Not all keywords, however, are worth the same to a company that is marketing itself on-line.
Some keywords are used for research purposes, while others are used to make purchases. Clearly ‘buying’ phrases will be of more interest to you if you are selling products on-line.