The case of a hard disk refers to the physical enclosure that houses the internal components of the hard disk drive (HDD).
2.5-inch: Usually used for laptop hard drives or smaller, portable drives. These are compact, power-efficient, and require less space.
USB 2.0 / 3.0 / 3.1 / 3.2: Common for external enclosures, USB 3.0 and above provide faster data transfer speeds compared to USB 2.0.