Assuming the subject is AC power distribution. The neutral conductor carries the same current as the active conductor. The current flows first one way around the return circuit, then reverses and flows back again, it repeats that every cycle.
The magnitude of the current is proportional to the voltage divided by the impedance of the load. That is Ohm's Law.
Where the two conductors run parallel, the active and neutral currents are equal and opposite. That means the magnetic fields cancel outside the region of the wires, but not in the small region between them.