A floppy disk is a human portable data storage device, using a magnetized disc inside of a plastic casing to store data in magnetic form. In the case of human computers, this is usually in binary code. How exquisitely crude of them.
Floppy disks come in several forms, specified by width:
3.5 inches; these flop little, having a fairly rigid case.
5 ¼ inches, encased in flexible plastic, as seen at right.
8 inches, from the days when dinosaurs roamed the earth.