Well, there are probably as many answers as posters, but my personal fave would be: A huge collection of networks all interconnected via fast (in most cases) wide area connections. Simple, huh?
<i>It's always the one thing you never suspected.</i>
yeah, geez. its just a big freakin network. no big deal. now tcp/ip - thats pretty amazing stuff. imagine developing a protocol that can manage hundreds of millions of users and not cause a massive meltdown. somebodies got a big brain over there at the pentagon!!!