HTML which is what makes titnernet what it is today was invented by Tim Berners Lee. He worked at CERN at the time 1989. Tinternet exised in one form or another for many years before this but it was all text based.
The internet is the physical network, pipes, themselves.
This was originally ARPA net, for military communication in the USA.
It was then expended to universities for collaboration.
Then, the general public.
As the above says, a 'system' that run on the internet is the world wide web, www. This was created by Tim Berners Lee. At the time, he was working at CERN (though not invented by CERN itself).