Iomega Zip drives are extremely popular because of their relatively low cost and versatility. Not only can a Zip drive be used as a backup unit, but it can also be used as another hard drive. Unlike tape backup units, you can use a Zip drive as though it is another hard drive. You can install programs on it, open files and work with them, move, rename, delete, and copy files and folders, and store backup data on it. Basically, with a few minor exceptions, whatever you can do with a hard drive, you can do with a Zip drive.
Zip drives use special cartridges that look a lot like floppy disks.
However, these cartridges hold 100 megabytes of data. If the data is compressed, it can hold almost 200 megabytes. This is probably the one major disadvantage to using a Zip drive as a backup unit. Zip cartridges don't hold enough data to make it practical as a backup unit. Iomega has recently marketed a Zip drive that handles 250 megabyte cartridges.