is there a differance between a micro sd and a mini sd?

Answer 1

YES, Micro SD is smaller than a mini sd.
you cannot use one for the other.

Answer 2

Yes, the difference is the size. There are 3 types of SD cards: standard, mini and micro. Micro being the smallest. A standard cell phone tends to use micro because of the size of the phone. A pocket PC uses the mini because it is a little larger than a standard cell. Cameras tend to use the standard. Some of the small pocket cameras might use the mini.

Yes, always check to see which format your device supports.