Basically the internet is a whole load (litterally thousands, if not millions) of computers networked together. All of which have online access and many are web servers and contain lots of data and information that the public can view through an internet browser such as Internet Explorer, Firefox, Chrome or Safari, to name a few.
Contrary to popular believe the internet is not a box which allows people browsing the world wide web to access. And no you cannot break the internet by typing internet into your address bar. I hope this has quickly answered your query of what is the internet.