A packet is a small, usually rectangular container made from paper or plastic. It can also refer to a set of data that is sent over a network in discrete pieces, called packets. These packets are used by computer networks and internet service providers to transmit information efficiently across the network. Each packet contains specific information about its destination address, source address, data, and error checking codes. Packets are reassembled at their final destination where they can be processed as a whole message or file.