#1
Can someone explain to me what taking your pickups out of phase does?

Both theoretically (as in, why does it work) and what it sounds like?
#2
I think it's like wiring it the opposite way so the pickup sounds a bit different, I've seen a thread on this saying jimmy page did this you should check in the thread list
#3
Basically the signal goes through the pickup backwards. This only has effect when using it with another pickup. For example, positions 2 and 4 on a strat.
These go to eleven...
#4
I'm not sure how much you know about electronics, but the basic theory of out of phase is that the two pickups are wired so that current runs the opposite way (out of phase) in one of the pickups and this cancels frequencies that are present in both pickups. You will end up with only the differences between the two pickups. I have never really tried but I hear it is best done with pickups that are different from each other (if they are very similar they will almost completely cancel each other out!) and it will produce a nasaly sound. You can find more info (and probably better answers too) if you look around in the customization forum (that's where i got my info from).