The A1010 is an external 3.5" drive originally built for use with the A1000, apparently the drive can be removed from the external unit and fitted internally in an A1000

External 3.5" drive called the Commodore A1011

The A1020 is an external 5.25" drive originally built for use with the A1000. Very few Amiga specific 5.25" drives exist, primarily because the only practical use for such a drive on the Amiga would be to read old PC formatted floppy disks. (Although Amiga formatted 5.25" can also be used)

Thanks to Peter Gordon, Richard Wagenfuehrer and CLS2086