A USB mass storage device is a portable storage solution that connects to computers and other devices via a USB (Universal Serial Bus) port. It allows users to easily transfer and store data, such as documents, photos, and videos. Common examples include USB flash drives and external hard drives. These devices are popular due to their convenience and compatibility with various operating systems, including Windows, macOS, and Linux. They typically require no additional software installation, making them user-friendly for people of all technical levels. Their compact size also makes them easy to carry and use on the go.