Now we will break down the links and discuss the general motion associated with each. To get a better understanding of each link try isolating it in your body and run through the range of motion for each.
The neck has two links: the base of the neck and the top of the neck or head. In a side profile each joint has a range of motion similar to a pin hinge with the pin running parallel to the ground and perpendicular to your view. In other words you are looking at the end of the cylinder of the pin.
The bottom neck link has a fair range of motion while the top neck joint has a much smaller range.