In 1969, U.S. Department of Defence sponsored a project. The name of that project was ARPANET.
ARPANET stands for Advanced Research Projects Agency NETwork.
At that time the aim of starting the project ARPANET was to connect computers present at different universities and U.S. defence.
In short time of starting the project named ARPANET, the engineers, scientists, students, and researchers who were the part of this project (ARPANET), began exchanging the data and messages on it.
After starting the exchange of the data and messages using the ARPANET from one computer to another. ARPANET started with a handful of computers. Later ARPANET expanded rapidly and in the mid 80's, another federal agency named National Science Foundation, created a new network having high capacity. The name of the network was NSFnet.
NSFnet was more capable than the ARPANET.
NSFnet only allowed the academic research on its network. NSFnet was not allowed any kind of private business on it.
Therefore, some private companies built their own networks. That networks were later interconnected to the ARPANET and NSFnet to form the internet.
At that time, it was the inter networking. In other words, the linking of these two and some other networks. In other words, the ARPANET, NSFnet, and some other private networks. That was named as Internet.
The ARPANET and the NSFnet were originally stops in 1990 and 1995 respectively. In other words, government stops funding for these networks. But the commercial internet services came into pictures, which are still running the Internet.