Hard disk drive (HDD) is a type of storage device that uses magnetic disks to store and retrieve digital information. It is one of the primary forms of secondary storage for computers, where data is stored for long-term use. If you have some data to store either from your computer or CCTV cameras, hard disk drive will do the task.

Hard disks come in various sizes, typically measured in gigabytes (GB) or terabytes (TB). The size of a hard disk determines how much data it can store. Hard disks are also available in different speeds. The speed of a hard disk affects how quickly data can be read and written to the disk.