Have you ever wondered what all those little boxes are when you defrag your hard drive? These boxes are clusters; they are storage units on the hard drive. This article will explain to you the concept of clusters. This applies mostly to the file systems FAT12, FAT16 and FAT32. FAT12 is only seen on floppy disks and very small storage medias, while FAT16 is the older version of FAT in the win95 days, and FAT32 is newer, and more in the Win98 days. Fat Stands for file allocation table. And no, there is no such thing as a SKINNY32 file system.