True North is based on the pole. Magnetic North shifts because it is based on and effected by the iron molten core of the Earth.
True North can be determined by the constellations, where Magnetic North cannot.
It is an interesting fact that however things shook out as the Solar System was forging, in relation to the rest of the galaxy, that we wound up with the Earth's rotational north pole pointing almost exactly at a prominent, easily-located star. It makes it very easy for anyone very far into the northern hemisphere, on a clear night, to determine true north.