Pole Vector constraints
 

What exactly is the point of pole vector constraints in animation? Am I supposed to do all my arm movements by moving around the control objects and the locators?

Pole vector constraints are commonly used to control things like knees and elbows. If you use IK on your character's arms, then pole vector constraints can come in handy. They'll help keep the elbows point where you want them to.

for ik that tends to be the case, the pole vector is used to control the orientation of the arm or leg, imagine a locator sitting right behind the elbow...and you have the pole vector constrained on the locator, when you move the locator up and down, the elbow should always point at the locator

posted at the same time i guess..and both good answers : )