Note for power users: Some modern emulators (like DuckStation) support .chd (Dreamcast compression), which offers slightly better compression than PBP but does not support multi-disc merging. If you hate disc swapping, stick to PBP.
Unlike the traditional or ISO formats, which are direct bit-for-bit mirrors of a game disc, a PBP file is a compressed container. It was reverse-engineered from Sony’s official proprietary format to allow users to convert their own physical libraries into a format that a PSP could recognize. Today, this format serves two primary purposes for emulators: saving space and simplifying file management. The Major Advantages PSX2PSP Tutorial - convert psx Games to pbp pbp psx roms work