A hard disk drive (HDD) is a type of storage device used in computers and other electronic devices to store and retrieve digital information. It consists of one or more spinning disks coated with magnetic material, where data is written and read by a moving arm. HDDs are known for their large storage capacity and relatively low cost compared to other storage options. HDDs are commonly used for storing operating systems, applications, and personal files. They are slower than solid-state drives (SSDs) but can provide significant storage space, making them suitable for tasks that require large amounts of data, such as video editing or gaming.