This was created for the Mac OS X operating system. Unlike the old operating environment versions, the font is stored in the thread of a data file instead of in resource threads. It’s been used as a container for TrueType fonts since 2009 after the release of Mac OS X 10.6, and is gradually replacing the TrueType Collection.
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 Today it has become obsolete and has been replaced by more flexible formats with DRM protection.