A brief history and guide to how the Internet works is available for dowload (at no charge) from MakeUseOf.com at this link. The image below is a diagram of the Advanced Research Projects Agency Network (ARPANET) as of December 1970. The was the world’s first operational packet switching network–the precursor to the Internet. The creation of this network was funded by the U.S. Department of Defense through the Defense Advanced Research Projects Agency (DARPA) and largely based on designs by Lawrence Roberts of the Massachusetts Institute of Technology’s Lincoln Laboratory. For more on ARPANET see this Wikipedia article.