There are many emulators which come and go on the Google Play Store, we’ve had Playstation 1, Dreamcast, Nintendo 64, Nintendo DS, and just about any retro console you can imagine, but never the PSP. PPSSPP is the first PSP emulator for Android, however the developers admit that it is still in extremely early stages, more of a prototype at it’s current version.
Like all mobile emulator apps, you’re required to download your own ROMS. You can probably find a lot of PSP ROMS by simply searching on Google, but be aware that not every game will work on this early attempt at a PSP port. I recommend downloading it as soon as possible, as it will probably be removed from the Play Store as soon as it begins to attract a lot of attention.