Hello and welcome to the forums.
In short, it can play PS2 and PS1 original games from any regions, master patched backups of PS2 games, PS1 backups, and it's probably compatible with the software that uses the expansion bay hdd, such as the japanese PSBBN for example.
Also it can't read Video-DVD.
A long and interesting read:
I have gone through all of my TEST units, and kept two of each for the archives. There are some very interesting differenced. There is the DTL-H10000 I have only seen one of these, it reads debugger on the back. 100volts. AC DTL-H10000, PSONE ONLY unit, cannot do DVD media, DVDR or...
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