The Macintosh came with a built-in 3.5" floppy drive - but in the days before hard drives being commonplace (unless you had a lot of money) having two floppy drives was a boon. M0130 was an external floppy drive for the original Macintosh, the follow-on 512K, the Mac Plus and the SE. It would not work with an Apple II.
The disk drive used 400K floppies formatted in the Macintosh File System format. And came in a nice neat beige box to match the original Mac.