A USB device is a type of hardware that connects to a computer or other electronic devices using a Universal Serial Bus (USB) interface. These devices can include items like flash drives, external hard drives, keyboards, and mice. They allow for data transfer and power supply between devices, making them essential for modern computing. USB devices come in various shapes and sizes, with different storage capacities and functionalities. They are designed for ease of use, often allowing for plug-and-play operation, meaning users can connect and disconnect them without needing to restart their devices.