The two top-voted answer includes WAAAAAY more information than the XKCD comic, so they're not really comparable. The third one explains it pretty simply.
That's exactly the point: some experts, when asked for a simple explanation, produce a huge info-dump in simplified terminology, and most experts thought that an appropriate response (see upvotes) - failing to realize that the result is anything but simple.
It takes a special skill to eliminate all the non-essential information and produce something truly simple to understand, like the comic.
Myself included. So many interesting topics to touch on when explaining something.
The only reason I ever manage to be short in text form is being able to go back and delete.
http://security.stackexchange.com/questions/55343/how-to-exp...