This format is used for storing photos taken with Swedish Hasselblad cameras. It has a RAW image file structure. It is saved without applying automatic corrections. Photographers can edit the 3FR photos by changing the white balance, color correction, and other parameters without sacrificing image quality.
This format was used for storing databases on the Pegasus and Palm PDA devices. Besides images, PDB allowed you to store tables, maps, e-books, and other data in a structured way. Today it has become obsolete and has been replaced by more flexible formats with DRM protection.