"Floppies" are low density magnetic diskette media. The magnetic ferric oxide material is applied over a Mylar disc with a metal or reinforced spindle in the center. Modern 3.5 in. floppy disks are encased in a firm plastic shell. At their introduction around 1987 some people referred to these as firmies to differentiate them from older, flimsy 5.25 in. and 8 in. diskettes.
At the time of this writing floppies are pretty much passe. New Apple iMacs don't even ship with floppy drives. Higher capacity "removable media" like Zip Disks, Orb Disks, and rewriteable compact discs, are slowly taking over. However, the seeming ubiquity of the 1.44MB floppy will probably save it from obsolescence for many years to come.