.APLIBRARY File Extension
What is an APLIBRARY file?
Library created by Aperture, a professional photo editing application; contains images edited in the Aperture application.
Aperture is an Apple developed professional photo editor. Some features include selective retouching, a variety of color filters, and advanced slideshows. You can edit photos from the iPhoto library with the Aperture program. You can also merge the iPhoto library (.PHOTOLIBRARY) and Aperture library but must be done in Aperture.
NOTE: Aperture was replaced by Photos in 2015.