It wasn’t always this way, and it was much more confusing; back in the day when we had floppy drives. We had floptical drives. A single unlabeled 3.5″ floppy disk could be formatted as 360 ...

Floppy Disk Formats 720KB 3.5" DS/DD 1.44MB 3.5" DS/HD 2.88MB 3.5" DS/ED (IBM only) 360KB 5.25" DS/DD 1.2MB 5.25" DS/HD DS = double sided DD = double density HD = high density ED = extra=high ...