Click on the Output File button to direct CMS to write
  output to a specified file; you must supply a file
  specification in the Output File field.

  If you omit the file specification in the Output File
  field, CMS creates a file in your default directory
  with the same name as the element.

  If you specify multiple elements (by using wildcards,
  a comma list, or a group name) and you do not specify
  wildcards in the Output File field, CMS creates successive
  versions of the file and places the files in your default
  directory.