+> "80 GB" iPod wrote:+
+> What does it expand? Is it just for more memory?+
No, it allows you to "expand" the features and ports of the machine. For example if you needed another FireWire port you could buy an ExpressCard FireWire Card., if you needed wireless internet you could get a subscription with Sprint, Verizon, ATT, etc and they would give you an ExpressCard wireless card to link up with the service. If you needed an e-SATA port you could buy and e-SATA ExpressCard. The options are many.
If you do ever need to buy an ExpressCard thought make sure it's OS X compatible. There are a lot out there that are Windows only.