A serial port is a communication interface that allows data to be sent and received one bit at a time over a single wire. It is commonly used to connect computers to peripheral devices, such as modems, printers, and scanners. Serial ports can be found on older computers and are often used for debugging and programming embedded systems. Data transmission through a serial port can be either synchronous or asynchronous. In asynchronous communication, data is sent without a clock signal, using start and stop bits to indicate the beginning and end of a data packet. This makes serial ports versatile for various applications, despite being largely replaced by faster interfaces like USB.