So looking at the Duelist precise strike it should be clarified a little better and I couldn't find an answer elsewhere so I call upon my ancestors knowledge
"Precise Strike (Ex): A duelist gains the ability to strike precisely with a light or one-handed piercing weapon, adding her duelist level to her damage roll.
When making a precise strike, a duelist cannot attack with a weapon in her other hand or use a shield. A duelist's precise strike only works against living creatures with discernible anatomies. Any creature that is immune to critical hits is also immune to a precise strike, and any item or ability that protects a creature from critical hits also protects a creature from a precise strike."
So how exactly does Precise Strike work?