When modeling an organic figure such as the human head and one that is going to have animated deformations via bones and or shape keys, it is important to understand some basics in mesh construction such as edgeloops , triangles VS quads, and poles. Gaurav Nawani has pointed us to an extensive tutorial / discussion on topology at SubDivisionModeling.com
A pole defined in the dictionary:
a. the point in a Cartesian coordinate system where the axes intersect.
b. Also called pole. The point from which rays designating specific angles originate in a polar coordinate system with no axes.
In this case it's when a vertice has either three or five (or more) edges radiating from it as in the example above.