A USB dongle is a small device that connects to a computer or other electronic devices through a USB port. It often serves various purposes, such as providing wireless internet access, enabling Bluetooth connectivity, or acting as a security key for software applications. These devices are typically plug-and-play, meaning they can be easily inserted into a USB port without the need for additional software installation. USB dongles are popular for their portability and convenience, allowing users to enhance their devices' capabilities quickly and efficiently.