tbtkdz:
You are correct: nothing about alternating current is fixed. It's alternating all the time.
Imagine the electrons sloshing back and forth in the wire 50 or 60 times each second. The movement of the electrons is the "current". Current is how much electricicty is moving.
The thing that is fixed is the voltage. Voltage is how much electricity is available, moving or not. On the neutral wire, voltage will always be the same. The current sloshes back and forth but voltage will always be the same as ground. We call that zero just so we have something to compare other voltages to.
On the hot wires, voltage goes up and down from positive to negative. The average voltage is what's given as the voltage but its actually going up and down all the time.
This is a little simplified, and lots of people are now going to tell you that the neutral voltage isn't always zero and that the voltage given isn't the average but the average of the square root of the square of the voltage and other stuff. Some are even going to get all fired up and type in capital letters or tell me that I'm going to get you killed but they're just trying to make it more complicated than it needs to be.
