Floppy disk drives read and write data to floppy disks. They are a legacy technology and only usually used with older equipment.
How they work
The data is stored on a flexible magnetic disk within a protective outer casing.
There were several sizes of disk; 8 inch, 5.25 inch and 3.5 inch however the larger sizes are all but obsolete.
Drives can be connected to a computer either internally or via USB.(<-- move the last sentence to How they work section).