Foobar is a slang term used in the IT world as a placeholder to refer to generic examples or temporary files or programs that are to be deleted. The technical term for a word like foobar is a metasyntactic variable*. These types of terms are used to name variables, programs or other parts of code .
It cames from the use of foo in a programming context is generally credited to the Tech Model Railroad Club (TMRC) of MIT.
For instance, a computer science professor may be discussing different file formats. In this case, he would call the generic-example file foo or foobar, then list the extensions associated with the file formats (e.g. foobar.txt, foobar.gif, foobar.exe, foobar.tar).
When foo or foobar is used, everyone understands that these are just examples, and they don't really exist .
*A metasyntactic variable is a placeholder name used in computer science, a word without meaning intended to be substituted by some objects pertaining to the context where it is used. Example, the word foo. Read more