An HDD (Hard Disk Drive) is a traditional data storage device used in computers and other electronic devices. It consists of one or more spinning disks (platters) coated with magnetic material, and a read/write head that moves over the disks to read and write data. HDDs are known for their large storage capacities and cost-effectiveness compared to newer storage technologies like SSDs (Solid State Drives). However, they are slower in terms of data access speeds and more susceptible to physical damage due to their mechanical parts. HDDs are commonly used for storing large amounts of data, such as operating systems, software applications, media files, and backups.