Commonly known as the place where information goes into and out of a computer, or both. For example, the serial port on a personal computer is where a modem or printer is connected.
On the Internet, "port" often refers to a number that is shown in a URL, following a colon right after the domain name. Every service on an Internet server "listens" on a particular port number. Most of these services have standard port numbers. Web servers normally listen on port 80, and the standard Gopher port is 70. (Services can also listen on nonstandard ports, in which case the port number must be specified in a URL when the server is accessed.)
Finally, "port" also refers to the act of translating a piece of software from one type of computer system to another, such as from a Windows program to one on a Macintosh.