The origins of the internet go all the way back to the dawn of electronic computing in the 1950's shortly after the introduction of the transistor. Vacuum tube computers were extremely useful computational devices, but they were so expensive to build, operate and maintain that their use was limited and isolated. With the advent of cheaper and more powerful solid state computers in the 1960's a large number of governmental, educational and commercial institutions adopted computer technology, and communication between those computers was inevitable.
Computerized Phone Calls
HTTP File Sharing
Privatization of Oversight
The Modern Internet
The earliest form of networking was of course simply using multiple terminals on one mainframe computer, and this practice went all the way back to the rather weak vacuum tube computers of the early 1950's. Communicating over longer distances though required the use of the telephone system. The oldest and simplest form of networking was simply for a phone call to connect one computer to another. This was very useful for sharing information, and the applications for this single link type of networking were quite widespread. A slight further sophistication was the use of an always running server that could be connected to at any time. The server had to be up and running all the time, or at least during certain regularly scheduled hours of operation. Other computers that connected with a phone call could be shut down when they were not being used. This eventually became known as a BBS (Bulletin Board Service) system of networking. Files and messages could be uploaded to the BBS server and would be available to view or download by other computers that connected to the BBS server. The limitation of this system was that the BBS server could only have a certain limited number of connections at any one time, so the larger the number of users the more cumbersome the system became.
The email system was apparently originally a U.S. Department of Defense program in the 1960's or early 1970's, but later became available to other governmental and educational institutions. The power of the email system was that it was based on a system of decentralized computing where any one of a large number of servers could handle email traffic so that a message would go through regardless of what was happening with any individual machine or network connection. The other feature of the email system that led to it's widespread use in the 1980's was that it was a scalable system that could smoothly grow to meet increasing demand. New servers coming online to handle increased traffic did not require that the existing servers change in any way. The only centralized management required was provided by the DOD in the form of assuring that each server had it's own unique "name" that was associated with the directions as to how to get a connection to that physical location. As with the original DOD program most network connections were over phone lines, but other dedicated telecommunications lines had been and continued to be used to carry large volumes of traffic between servers.
As the story goes the internet was born at the Stanford University in Palo Alto, California when a team of physicists decided that they needed a better way to share files than could be provided by the email system. Email had been a popular and successful means of sharing data and collaborating over long distances, and had apparently been extensively used by Stanford physicists working at the Stanford Linear Accelerator (SLAC). Email was great in that it could nearly instantly disseminate information to a large number of recipients located all over the world, but file sharing with email was limited in that the larger the number of people involved with a project the more cumbersome the lists of messages to dig through became. The basic problem was that the file had to be sent to each potential recipient even though not everyone was interested in each individual message. The SLAC physicists simply wrote some software for a new type of file transfer protocol that would run on the existing email system. This new type of file transfer system was a further sophistication of decentralized computing, and eventually became the Hyper Text Transfer Protocol (HTTP) system for handling files on the internet.
The basic idea was that a file could be posted to a server so that anyone could download and view that file from any location. This is similar to how the old BBS servers worked, but the difference is that the decentralization of the email system remains. If the BBS server goes down the whole system is rendered inoperable. Just as email messages are re-routed if any individual server goes down, files available for HTTP transfer can be stored on multiple servers, and one of those servers going down or any one network connation being disrupted does not affect the smooth and seamless operation of the system. The advantage of HTTP over using email was simply that an extremely huge number of potential recipients (anyone in the world with a connection to the email system) could have access to any particular file without that file having to be sent individually to all those potential recipients.
Essentially the SLAC physicists had hacked a DOD computer system to create the internet, and eventually the DOD got out of the roll of providing everyday management of lists of unique names of servers. The system of Domain Name Servers (DNS) that assures that each domain name is unique and maintains directions as to how to find the files associated with that domain name has for many years been managed by a governing body made up of industry professionals. This might not be quite as robust as the DOD management, but up to this point it has continued to function. The internet is a totally decentralized system that can grow and evolve over time, but it still does inherently require some stabilizing force to prevent destructive change. In the absence of any management of the DNS system the internet would continue to function for some period of time, but conflicts would eventually develop over who owns what name and the system would slowly degrade to the point of totally non-functionality.
Although the initial construction of the system of software that became HTTP occurred earlier it was not until the early to mid 1990's that the internet really took off as a significant commercial force. By the late 1990's most mail order companies were offering online catalogues and online ordering, and a large portion of all businesses were using the internet at least for advertising purposes.
The use of the internet for business and commerce provided a huge push towards higher levels functionality of websites. The HTML (Hyper Text Markup Language) originally developed to go along with HTTP file transfers was a powerful and easy to use programming language, but it was also directed at more open forms of communication involving educational institutions and formal peer reviewed science. Providing customer interactivity and security for transfer of funds required ever increasing levels of sophistication in the programming languages used to drive the internet. The entire internet is still ostensibly email and HTML based, but the level of additional sophistication supported by most servers and web browsers is substantial.