A magazine on disk. These have also, at various times and by various people, been referred to as "Magazines On Disk" (obviously), "Monthly Software Collections", "diskmags", and "magazettes" (an attempt at a word combining "magazine" and "diskette", used early in the history of Softdisk, but which never caught on).
Two basic varieties of diskmagazines are the ones that are complete in themselves (e.g., have all the editorial material on disk), and the ones that accompany paper magazines to supplement their content. (The ubiquitous AOL disks, frequently bundled with magazines of all sorts, don't count!)
Prior to diskmagazines, there actually were a few cassette magazines, to be loaded from tape on early home computers like the TRS-80. Early disk and cassette magazines were intended as an improvement on the old style of computer magazines that were full of program listings in BASIC for the user to type in themselves.
The rise of the CD-ROM caused some temporary invigoration to the moribund diskmagazine genre, as it allowed more multimedia-intensive publications than were possible on floppy disk, but in the long run, the presence of the Internet, with all of its ever-changing multimedia content available free, will probably doom any computer publication on physical media to failure.