I was wondering what exactly the difference between cf and sd cards is. Is one used for ram and the other for storage? Or are they just two different types of storage cards?

The difference is no more or less than this:

They are two physically different hardware interfaces to peripherals controlled respectively by two different organizations.

The SD Association is much more tight with specifications, as a result, the SD slot in the Zaurus isn't useful for much besides flash memory, whereas CF is a more open standard, so a lot more different kinds of devices can have open source drivers.

Also, the CF standard is physically larger than SD, so it can handle things that just can't "fit" into an SD card.

And yes, they can both just be storage cards or they can be devices (such as wifi cards); neither has anything to do with RAM on your Zaurus, they are completely separate.
The Zaurus only really supports CF device cards (not sure about the terminology here) as the SD stuff is relatively closed as DrWowe says so there aren't (m)any drivers available for Linux.


Si

Worth mentioning - Most Zaurus users will eventually end up buying a 1 GB SD card because the CF slot will be taken up by WI-FI or Bluetooth CF cards.

Thanks for the info.