In normal parlance there isn't one, and in Solaris the devisions of a disk are called slices.

The real difference is more subtle. A slice is what in the windows world would be called a "primary partition", ie it is a physically bounded area of disk. A partition is actually a logically, not physically, bounded area of disk which resides within a slice again you don't normally see any difference in Solaris, but in the windows world the "secondary partitions" all reside within one slice on disk.