A serial port is a communication interface that allows data to be transmitted one bit at a time over a single channel. It is commonly used to connect devices like modems, printers, and computers. Serial ports can be found in both hardware and software forms, enabling devices to communicate effectively. Typically, serial ports use a standard called RS-232, which defines the electrical characteristics and timing of the signals. They are often identified by their 9-pin or 25-pin connectors. Although less common today due to the rise of USB and other interfaces, serial ports are still used in various applications, especially in industrial settings.