Magnetic and geographic poles
Near to the Earth's geographic North Pole there is the magnetic pole which we can picture as being one end of a huge, imaginary bar magnet which passes up through a north–south axis of the Earth.
Suppose that you are using a compass and the needle settles down along a north–south line. The north pole (or north-seeking pole) of the compass points roughly (but not exactly) towards the geographic North Pole of the Earth. This makes sense.
However, if you stop to think for a moment, if we define the end of the compass needle which points north as the north pole of a magnet, then it must be attracted to a south pole. The inescapable conclusion is that the magnetic pole in the Northern Hemisphere of the Earth is, in fact, a south pole. On first meeting this concept, it seems very strange indeed, but it follows from the definition of the poles of a compass needle.
That's not the end of the story, of course. The magnetic poles have not remained in the same place. So both declination and inclination have wandered. The Earth's magnetic field is not static.