The starting position and the seven cardinal movements of the baby as it descends through the birth canal. The small pictures show the position of the baby’s head, as if you were looking up the birth canal.
I'M ALMOST 7 MONTHS! The Pregnancy Survival Guide for First-Time Dads - Primer. This site does a great job of discussing it from a man's pov while staying classy and sophisticated. The article is totally worth reading.