Rules for data transfer, called protocols, govern how information is transmitted on the Internet.
The Internet is based on a set of protocols known as the TCP/IP protocol suite and uses a system of packet switching for data transfer. Growing from research originally funded by the US Advanced Research Projects Agency in the late 1960s and early 1970s, the Internet was designed to be highly robust in case one section of the network (or a computer host in the network) became inoperable.
Packets could simply be transmitted over another route through the network, because no one network path was essential (unless, of course, it was the sole link to a given computer host). A set of data can be sent over the Internet by being broken into discrete packets. These packets can each be sent (or re-sent, in the case of data corruption or loss) over different routes on the network, and assembled (based on information encoded into the packets) in their proper order upon arrival at the destination.