Filters are used to narrow down the files to be tagged to only the relevant ones, without having to do the selection manually in Finder.
For example, if you have a folder that contains image and video files and you want to tag images yellow, but videos orange. Instead of manually selecting the image files, tagging them, then selecting the video files and tagging those, you can just drop the folder, select Image from the filter drop down, execute, then select Video and execute again. Of course, this is a simple example, but it should explain the power of that feature.
Select a file type from the filter drop down to filter the files to be tagged.
The following file type categories are available. They are like the ones that you can choose in a folder search in Finder.
The option Any File is the default option and tags all regular files. File aliases and folders are excluded. You can include file aliases by enabling the Include File Aliases switch.
This option behaves the same as Any File, but also tags folders. If you dropped a folder, the enclosing folder is not included, only subfolders if any. Note that file packages are not traversed, that means only the root folder of a package is considered.
Any documents like Word or Pages.
If this option is selected, only folders are tagged.
Any regular image files, like PNG, JPG, GIF. Custom image formats by Photoshop or Pixelmator are not recognized.
Any music file like AAC or MP3.
Any presentation files like PowerPoint or Keynote.
Any PDF files.