A physical tape library uses real magnetic tape cartridges and drives. A virtual tape library (VTL) is a disk-based appliance that emulates a physical tape library closely enough that backup software sees what looks like the same cartridges, slots, and drives, while the data actually lands on disk. A VTL is typically faster for both backup and restore, while physical tape keeps the ability to remove a cartridge and take it fully offline and offsite. See the full VTL vs. physical tape library comparison.
