The HoudahSpot Info pane shows all metadata Spotlight has recorded about a particular file. This includes generic attributes (file name, dates, etc.) as well as custom attributes filled in by the Spotlight importer responsible for indexing the file. You can use any of these attributes to find similar files.
Example: You are searching for a photo. You have set up criteria based on file type and creation date. Still you get too many results. You notice that the Info pane lists the “Device Model” of the camera used. You can thus narrow down the search to only images taken by the same camera model: Drag the relevant row from the Info pane to the Refine pane.
Rather than update the search – which has it start over – you can also filter the current results by checking boxes next to attributes in the Info pane. It’s like telling HoudahSpot:
Show me only files like this one