 The words foo and bar are good examples as they are used in over 330 Internet Engineering Task Force Requests for Comments, which are documents explaining foundational internet technologies like HTTP (websites), TCP/IP, and email protocols.By mathematical analogy, a metasyntactic variable is a word that is a variable for other words, just as in algebra letters are used as variables for numbers.Metasyntactic variables are used to name entities such as variables, functions, and commands whose exact identity is unimportant and serve only to demonstrate a concept, which is useful for teaching programming.