NASCAR Racing: Passing Under Caution, running order, pit road

Question
I'm a relatively new NASCAR fan, so forgive me if this seems to be an ignorant question. I've always been under the impression that once the caution comes out, drivers are required to maintain running order (not pass other drivers) until after restarting. However, I've noticed recently that some drivers pass each other. When is this allowed? Thanks for your help!

Answer
Hi Christy,

The only ingnorant question is "Why do people bother to watch NASCAR?...it is so boring..."  
  Anyway, the drivers are required to maintain running order and pace speed under caution.  
  If two drivers were racing side by side and whoever was in front when the caution came out was not clear, then that could be a circumstance for two drivers to swap spots.  
  The first car one lap down gets the "free pass" and gets to pass the field of cars and actually speed back around the track to the back of the lead lap cars.  So that's another situation.
  And sometimes NASCAR gives out on-track penalties and tells drivers to fall to the back of the pack.  Such penalties could be for pit road violations or aggresive driving
  But the most common thing to see is that while the lead lap cars line up to the outside, the lapped cars line up for restarts on the inside.  And these can occasionally come from the back of the pack.  So i think that may be what you see on the tv.
  Hope i helped!
  Coy Jordan