In order to store digital media such as photos, audio files, and movies on your PSP, you need a memory stick. Sony offers two official memory sticks that can be used with your PSP: the 2gb Memory Stick Pro Duo and the 4gb Memory Stick Pro Duo.
Also note that memory sticks from other manufacturers such as Scandisk may be used successfully to store media on your PSP, but it is not recommended by Sony to use these third party products (do so at your own risk - may potentially conflict with the terms of your warranty or harm your device).
