Of the metasyntactic variable
s, which are generally used as placeholders when describing a system, or as temporary names for works-in-progress, "foo" and "bar" are probably the two most popular, followed closely by "baz".
For instance, it could be described that a function "foo" takes two integer argument
s, "bar" and "baz", and "foo" return
s their sum. In doing so, metasyntactics have been used to describe a concept wherein the actual names are of little importance.
Read more on metasyntactics