Can you give me the idiot's guide explanation?
See
http://simple.wikipedia.org/wiki/Quantum_entanglement
http://objectmatrix.spaces.live.com/blog/cns!BA7DBC3966A6FA91!1870.entry or
http://searchcio-midmarket.techtarget.com/sDefinition/0,,sid183_gci341428,00.html
Basically, imagine you have 2 particles. Say electrons, for arguments sake.
The 2 electrons form part of a system, like an atom. We know from observation of this particular type of system, that one electron spins one way, the other spins in the opposite direction.
The moment we observe one electron spinning clockwise (relative to our point of observation) we automatically know (without observation) that the other one moves counter-clockwise.
It doesn't matter how separated these two particles are, they can now be separated by light years, and they still share this relationship. The moment we observe one spinning clockwise, we instantly know the rotational state of the other one.
This sounds like mere common sense, until you apply that other nonsensical quantum law, the law of superposition which states that the particles actually have no rotation at all until we observe it. It's like Schrodinger's cat - it is both spinning both ways and not spinning at all in a kind of 'nether' state, until it is observed.
If that's true, then it's almost
like there is some kind of instantaneous transmission or communication between the two particles, regardless of distance between them - though quantum phsyicists state there is no information shared in this way.
At this point, my head starts to hurt normally.