Keywords are words or phrases that describe the content. They can be used as metadata to describe images, text documents, database records, and Web pages. A keyword is a word, a keyword phrase a phrase, that a person enters into a search engine like Google or Bing, or a social network such as Facebook, Twitter, or LinkedIn. Keyword phrases of three or more words or truncated sentences are known as long-tail keywords. Keywords are used on the Web in two different ways: 1) as search terms for search engines, and 2) words that identify the content of the website. A keyword phrase is generally two or more words that are used by advertisers in search engine optimization, or by visitors who are using search engines in a desire to find information based on that particular phrase.