Q: whats a umd or a meomary stick also whats the diffrence
A: On the PSP the UMD is the disk with the game on it that you put into the back of your PSP. The PSP reads the the game and let's you play it. A memory stick is completely different from a UMD. The Memory stick is a stick that you put into the side of your PSP to save your game data, custom themes, music, and videos. Memory sticks are much smaller than the UMD and the UMD has white on the outer part. When you play games make sure you have a memory stick or else you can't save your games. Lastly, memory sticks come in different sizes for example, my PSP came with a 1 gigabyte memory stick. It also came with a Daxter UMD and Family Guy: Freakin' Sweet Collection UMD.