I was looking through some files to try and free up some HD space, and there are two different file sizes on each file. One is called simply "Size" and the other is called "Size on Disk". The "Size on Disk" is always just slightly higher, depending on how big the "Size" is.
Ex: Size = 10 kb
Size on disk is probably around 13 kb
size = 123 MB
size on disk is probably around 135 MB
what the heck is the difference? why are they different?