Net neutrality is a complicated and controversial subject. The principle states that if a given user pays for a certain level of Internet access, and another user pays for the same level of access, then the two users should be able to connect to each other at the subscribed level of access.
Basically, net neutrality calls for an open and non-tiered network. The world's systems of roads is a great metaphor for the Internet. Just like there's no simple way to shut down all the roads in the world, there's no simple way to turn off the Internet.
By imagining the Internet as roads, we can envision each packet of data as a car or truck traveling the highways and byways. Just as a car or a truck carries a "payload", a network packet carries a payload of data.
Using this metaphor, net neutrality means that cars get to drive on the roads with the same priority (speed) that the surrounding traffic will allow. No one's allowed to travel faster than the speed limit simply by paying more.
Openness is also a huge part of net neutrality. The biggest difference between a public toll booth on a road and an outlaw warlord collecting a bribe at a roadblock is openness. We all know that the police and the fire department get to break the speed limit in the line of duty because it makes sense and it's done openly; but it's not OK for a police officer to speed, when off duty, in order to make it to a personal appointment.
Being open also means that a network's owner cannot secretly block, filter, or divert packets because it suits them.
Image what the U.S. road system would be like if large corporations could pay for faster, shorter, and better "Lexus Lanes", while private citizens were forced to use lower quality roads.
Joe Moreno (http://bio.joemoreno.com) lives in Carlsbad, CA. and provides cloud computing and WebObjects consulting services to businesses. You can follow him on Twitter @JoeMoreno or reach him at (760)444-4721.