The fundamental unit of transmission of data on the Internet. Everything sent over the Internet is subdivided into individual packets and given a destination IP address that the packet will be sent to. Let's say that you want to send 250 cookies to a friend as a gift. However, you have boxes that can only hold 100 cookies each. Therefore, you must subdivide the cookies into three separate boxes, then put your friend's address on each box.
For this reason, the Internet is known as a "packet switched" network, in contrast to the phone system which is known as a "circuit switched" network. A circuit is much like a stream of water continuously flowing. A packet is like a block of ice. Either way, all you see is a bunch of water on the other end. But the Internet first freezes it, cuts it into blocks, ships them across to your computer, which then melts them all back together again.
