A mechanical hard drive (HDD) is a type of data storage device that uses spinning disks coated with magnetic material to read and write information. Inside the drive, a moving arm accesses the data on these disks, allowing for the storage of large amounts of information at a relatively low cost. HDDs are commonly used in computers, servers, and external storage devices. While they offer significant storage capacity, they are generally slower than solid-state drives (SSDs) and can be more susceptible to physical damage due to their moving parts.