You can filter the results based on a number of criteria using the Filter menu.
When browsing by folder, you can choose whether to show just the photos in the selected folder (the default), or photos in all subfolders.
When browsing by category, you can choose whether to show just the photos in the selected category, or photos in all subcategories (the default).
For the remaining items, choosing a filter will remove some photos from the search results (whether you're browsing by folder, category, or search). A reminder that a filter is selected will be displayed in the status bar. To remove a particular filter, choose "All Photos".
You can show just JPEG, GIF, TIFF, PNG, and PDF image files. This filter checks for particular file extensions, and only applies when browing by folder.
You can show photos with at least a certain rating, or unrated photos.
You can show photos taken in the current calendar day, month, or year.
A photo probably has a date, a place, and some people and/or things. Therefore, you can show photos with or without a date, place, or person/thing category.
You can show photos that are backed up to disc, or not backed up.
You can show photos that are shrunk, or full-resoltion.