@hat is difference between dismissViewControllerAnimated and popViewControllerAnimated

I am working in IOS 8. I am using Both the push and modal segues in My project. also unwind segues and Popping a view controller from navigation controller. But What I want to know is when I push through Navigation controller but Instead of using popViewControllerAnimated method to go back to previous view I used dismissViewControllerAnimated and it worked (I used it because My pushed ViewController was also embedded in another Navigation Controller). So what is difference behind the Scene does it off load it from the parent navigation controller's stack ? Also which one is efficient in this scenario.