What's an emulater, and HOW DO I DOWNGRADE ON PSP????

Answer 1

An emulator allows you to play game roms of other gaming system on PSP. For example, a Gameboy Advanced emulator will enable you to play GBA games on PSP.

As you probably know, in order to run an emulator on PSP, your PSP has to be homebrew enabled. In order to do so, you need to downgrade your PSP to firmware version 1.50.

Currently, firmware below 3.03 can be downgrade to 1.50. You can find more information on how to downgrade at http://www.psp-hacks.com/.

However, word of warning. Downgrading is very risky. If you don't know what you are doing, it will make your PSP usless (they call it bricked). If you are newbie, I would not do that if I were you.