Anyone who has ever spent some time playing on an emulator knows what a savestate is. They're useful and can be invaluable when you're in a very difficult area of a game, but commercial games and consoles don't usually support the savestate feature.
All that may change if this new experimental plugin from Dark AleX proves feasible. The plugin itself is called PspStates and, as you may have guessed from the title, it lets you create savestates while playing games on your PSP Slim. It was originally thought to be included in CFW 4.00 M33, but Dark AleX says that PspStates was never intended to be released as part of M33CFW but as a standalone plugin instead.
More at the source.