These are simply portable hard disks or tapes and a hard- or tape-drive in your computer where you plug them in. Copying to these to back up your system (in case the hard drive fails or becomes corrupt (due to a power surge, power outage, physical damage like water or soil, etc.)) is much simpler than copying to a large number of floppies.
Backing up files usually takes quite a bit of time, so it's something you'll want to do during non-business hours (like night time), so simplifying it to a one-step process is probably a good idea.
More information on backups is under the "Software Requirements" section.