External storage devices are hardware components that allow users to store and retrieve data outside of their main computer system. Common types include USB flash drives, external hard drives, and memory cards. These devices connect to computers or other devices via ports like USB or Thunderbolt, providing additional space for files, photos, and backups. These devices are useful for transferring data between different computers or for creating backups of important information. They come in various sizes and capacities, making it easy to choose one that fits specific storage needs. Popular brands include Western Digital, Seagate, and SanDisk.