The Internet was a computer network established by the US Department of Defense in 1969, through an ARPA agency project that developed a network called the ARPANET (Advanced Research Project Agency Network), where they demonstrated how the UNIX-based computer hardware and software.
The initial purpose of the construction project was for military purposes. At that time the US Department of Defense created a scattered computer network system by connecting computers in vital areas to solve problems in the event of a nuclear attack and to avoid the occurrence of centralized information, which in case of war can be easily destroyed.
ARPANET initially linked only 4 sites - the Stanford Research Institute, the University of California, Santa Barbara, the University of Utah, where they formed a unified network in 1969, and in general the ARPANET was introduced in October 1972. Soon the project growing rapidly across the region, and all universities in the country want to join, thus making ARPANET difficult to organize.
Therefore the ARPANET was split into two, the smaller military "MILNET" and the new "ARPANET" for non-military purposes such as universities. Combined both networks eventually known as DARPA Internet, which then simplified into the Internet.