Explain awakeFromNib and initwithFrame: usage

I am going through the Stanford iPhone dev lectures on iTunes and ran into this in Lecture 5.

We are trying to ensure a redraw will be done when the device rotates. I have two questions related to this:

1. What is awakeFromNib? There's no call to this method in the rest of the code. How was it triggered?
2. What does the codes inside initwithFrame: do?

.

-(void)setup 
{
      self.contentMode = UIViewContentModeRedraw;
}

-(void)awakeFromNib
{
    [self setup];
}

-(id)initWithFrame:(CGRect)frame
{
     self=[super initWithFrame:frame];
     if (self) {
        [self setup];
     }
     return self;
}