When a person poses for their portrait, sometimes, you only see the side of them they want you to see.  As a photographer, it is my job to go beyond what's on the outside, whenever possible.  In addition, if I am fortunate enough to sneak a portrait of someone when they least expect it, I capture far more.  A portrait should not only reveal what is behind someone's eyes to be great, it should also give you a glimpse of their soul.