How do the NFL playoffs really work?

I have freinds that say the Packers still have a chance to play Atlanta on the 15th. If you go to NFL.com and look at the brackets they have set up, it would appear that only the winner of the Seahawks and Saints game would be playing ATL on the 15th. I am confused as to how Packers would have a chance to play when their bracket says they would be playing the Bears... SO CONFUSED!