This is a positive gesture used by women and gay men in courtship. The face is like a plate for the man to admire.
Authority people like to use this. It gives the image of superiority, power and confidence. The delicate visceral area is exposed.
This is a signal of frustration and an attempt at self control. It is almost an attempt to stop the other arm from striking out. The higher up you grip the other arm / wrist, the more frustrated you are.
Click here to continue on to the head.