What is Palaeolatitude; virtual geomagnetic pole?

The palaeolatitude of a site is the latitude $\lambda$ given by its mean inclination through the dipole formula, $\tan I = 2\tan\lambda$. The virtual geomagnetic pole (VGP) of a direction $(D, I)$ observed at a site is the north pole of the geocentric dipole that would produce that direction there.