External hard drives provide a quick and easy way to expand your PC or laptop storage. They can feature single or multiple drives, connected via USB, eSATA, or Thunderbolt. Portable USB drives are powered by the host, while larger desktop drives require a separate power supply. Capacity and scalability depend on the drive type—1.8in, 2.5in, 3.5in, or M.2, with HDD or SSD options. Choose the configuration that best suits your storage needs.