A method of distributing data over a network first developed by Leonard Kleinrock between 1959 and 1962, that was used on ARPANET. In packet switching, information is broken into small segments of data known as packets and then reassembled when received at the destination. Packet switching helps prevent any small information sent after larger information from having to wait until the larger information has been sent. When information is broken into packets, the information size and speed of the line is what determines how fast it takes to send over a network and not the order in which it was sent.
Before packet switching if your data were number five in the above example, you would have to wait for 1, 2, 3, and 4 to complete before any of your information would be sent. However, with packet switching each segment of information is broken into packets, so with a small amount of information you only needed to wait a short amount of time. In the above example, even though it is first in the list it would take the number one much longer to complete because it is bigger, which means it is broken into many more packets.