(bashref.info)The Directory Stack

   The directory stack is a list of recently-visited directories.  The
`pushd' builtin adds directories to the stack as it changes the current
directory, and the `popd' builtin removes specified directories from
the stack and changes the current directory to the directory removed.
The `dirs' builtin displays the contents of the directory stack.

   The contents of the directory stack are also visible as the value of
the `DIRSTACK' shell variable.