A group of words that as accurately as possible describes everything about the subject matter. This could either be used in a search engine or could be used as tags to a particular item. For example: “weapons technology secret program” is an example of a set of keywords you would use in a search engine. Tags are also an example of keywords. When you tag a picture in Flickr you are making it easy for others to quickly find your picture when they search for matching or similar words.