I suppose you could explain it in abstract terms without knowledge of a computer (ex. the internet is a wonderful place where people can connect from all around the world in the blink of an eye), but that wouldn't really convey the nature of it.
The question is also open to further interpretation: Is it, what the internet is, what it can do, how it works, what it means to society, or something else? There are many ways to "explain the internet" to someone with no knowledge of computers, but to explain how it is, or how it works, they must understand what a computer is.
