In order to store more data, a disk actually has multiple platters.
As opposed to a "floppy disk", which stores a lot less, and has flexible platters made of soft plastic instead of steel.
Let's take out the floppy disk drive:
Here's where the floppy disk is inserted:
Unlike the hard disk/drive, floppy disks are "removable" -- the disk and drive mechanisms are separate. So you can have any number of recording surfaces (floppy disks) to use with the same electronics (the floppy disk drive).
Whereas with hard disks, the hard disk and the hard disk drive are a unit.