Disks or diskettes come in two different types. Floppy disks are flexible plastic with a special metallic coating on them. They come in two sizes. 5 and a quarter inches wide, and three and a half inches wide. The three and a half inch disks are protected by a hard plastic case, while the five and a quarter inch disks are usually placed in a paper sleeve.
Floppy disks are removable.
They can be taken out of the computer and stored or moved. A hard disk stores information on a rigid metal or glass disk. Information can be packed very tightly on hard disks. While a floppy disk generally can't hold more than two megabytes of data, hard disks easily hold a hundred times that much information. Many hard disks actually contain several rigid disks arranged on top of each other like a stack of pancakes.