Packet: A chunk of data. The TCP/IP protocol breaks large data files into smaller "packets" for transmission over the Internet. When the data reaches its destination, the protocol makes sure that all packets arrived without error.

Packet Switching: A method of moving data around the Internet that allows many people to use the same lines at the same time. In packet switching, all data being transferred from a machine is broken into packets, with each packet having the address of its origin and destination. This enables packets from different sources to be simultaneously transferred, sorted and directed on the same line.

Password: A code used to gain access to a locked system. Effective passwords should contain both letters and non-letters and not be common or easily guessed words.

Ping: A program for determining if another computer is presently connected to the Internet.

Pixel: Shorthand for "picture element", a pixel is the smallest unit of resolution on a monitor. It is commonly used as a unit of measurement.

PKZIP: A widely available shareware utility that allows users to compress and decompress data files.

Plug-in: A small piece of software that adds features to a larger software application. Common plug-ins are those for web browsers (RealAudio, QuickTime, etc.) or graphics programs (Kai's Power Tools, DigiMarc, etc.)

POP: ("Point Of Presence" or "Post Office Protocol") - A Point of Presence usually refers to a city or location where a network can be connected to. For example, if an Internet company says they have a POP in Vancouver, this means they have a local telephone number in Vancouver and/or a place where leased lines can connect to their network. A second definition, Post Office Protocol, refers to the way email software (such as Eudora) retrieves mail from a mail server. Almost all SLIP, PPP or shell accounts come with a POP account as well.

Port: (3 definitions) - First and most frequently, a port is where information goes into and/or out of a computer, such as the serial port on a PC. Secondly, a "port" often refers to the number appearing after the colon (:) in a domain name, such as http://www.example.com:7000/. Thirdly, to "port" something refers to translating a piece of software from one computer platform to another (for example, from Windows to Macintosh).

Posting: A single message entered into a newsgroup, mailing list, or other communications system.
 

PPP: (Point to Point Protocol) - The protocol that allows a computer to use a phone line and a modem to make TCP/IP connections and connect to the Internet.

Protocol: Computer rules that provide uniform specifications so that all computer hardware and operating systems can communicate with each other.

PSTN: (Public Switched Telephone Network) - The regular telephone system.