An interface on a computer to which you can connect a device. Personal computers have various types of ports. Internally, there are several ports for connecting disk drives, display screens, and keyboards. Externally, personal computers have ports for connecting modems, printers, mice, and other peripheral devices.
Old personal computers used to come with a serial RS-232C port or RS-422 port for connecting a modem or mouse and a parallel port for connecting a printer. On PCs, the parallel port is a Centronics interface that uses a 25-pin connector. SCSI (Small Computer System Interface) ports support higher transmission speeds than do conventional ports and enable you to attach up to seven devices to the same port. Nowadays all these ports are replaced with USB ports which emulates serial or parallel ports.
Network Port: A network port is a number that identifies one side of a connection between two computers. Computers use port numbers to determine to which process or application a message should be delivered. Port numbers are similar to address of a house.
Transport layer protocols, such as the Transmission Control Protocol and the User Datagram Protocol (UDP), specify a source and destination port number in their headers. A port number is a 16-bit unsigned integer, thus ranging from 0 to 65535.