A parallel port is a type of interface found on computers that allows for the simultaneous transmission of multiple bits of data. It is commonly used to connect devices such as printers, scanners, and external storage devices. Unlike serial ports, which transmit data one bit at a time, parallel ports can transfer data in parallel, meaning multiple bits are sent simultaneously. This makes parallel ports faster for transferring large amounts of data, but they are less commonly used in modern computers due to the rise of USB and other more versatile interfaces.