A Zip disk was an advanced version of the floppy disk developed by Iomega. The disk needed a special drive called the Zip drive in order to be used. Zip disks were available in 100- and 250-MB capacities and were used to store, share and back up large amounts of data, which was not possible with ordinary floppy disks. With the introduction of new and better storage mediums such as memory sticks and DVD-RWs, along with higher capacity hard disks, the Zip disk became less favored and eventually disappeared from the market.
Techopedia explains Zip Disk
Zip disks looked similar to floppy disks, but were slightly larger and thicker, and had stronger plastic casing, making them easier to store and handle. Like floppy disks, Zip disks were lightweight, portable and relied on magnetic storage techniques. The magnetic coating used in Zip disks was of higher quality than that used in floppy disks, and they could store more data than floppy disks.
Zip disks were PC and Mac compatible. They were usually used as secondary storage devices. Zip disks had faster data transfer rates and faster seek times than floppy disks. At the height of their popularity, they were preferred for backing up hard disks and for transferring large files, especially image files. They were less vulnerable to damage and were much stronger and more durable.
Zip disks, however, were expensive in comparison to floppy disks and needed a Zip drive to be used. Zip disks were also vulnerable to click-of-death issues, resulting in data loss.