A USB serial cable is a cable that connects a computer or other device to a serial port on another device. It is used to transmit data between the two devices. The cable has a USB connector on one end and a serial connector on the other. The USB connector is typically plugged into a USB port on a computer, while the serial connector is plugged into a serial port on the other device. The USB serial cable allows for faster and more reliable data transmission than traditional serial cables. It is commonly used in industrial automation, medical equipment, and other applications where data must be transmitted between devices.