In the context of the PlayStation 3, a "PKG" file is an installation package similar to an .exe file on Windows. While the PS2 originally used DVDs and the PS3 used Blu-rays, the PlayStation Store sold "PS2 Classics"—digital versions of PS2 games wrapped in a specific format to run on the PS3 hard drive.
It is important to note that PKG is not the only method. Advanced users often prefer converting PS2 ISOs and loading them via or the ps2netemu emulator (particularly on backwards-compatible units). This method allows users to run the raw game disc image without installing it as a package, which offers slightly better compatibility on specific consoles. juegos pkg ps2