Look at this picture, which a student took of me in a class the other day:

Michael Teaching

Can you see how she turned her flash behind her, so it aimed at the wall above her, which in turn lit me with soft, gentle light? Otherwise, if she had aimed it at me directly, we would have seen all the things that people hate in flash:

• oily skin
• flat face
• dark background
• overexposed subject
• shadows under the chin

Instead, we get soft, natural looking light.  And it’s easy: turn the flash so that the light bounces behind you. With TTL, it’s easy: the camera does the math. You just push the button.