How does laser cooling work?

Before clicking on the video, I thought "oh my, just another attention seeking chick, saying stupid things about stuff she finds sciency". But I was curious about "laser cooling" so I watched it. To my surprise, a nice intelligent lady showed up and spoke about the issue. And then all of a sudden Veritassium! That means she's doing more awesome stuff. 
Kudos to you Science Girl! You brought back the hope :) Keep up the good work!