Black thinks he can break out easily with the - combination. But White has a good reply using an inducing move (in fact, it is the only way to get a good result here):
is the key move. This may look subtle, but in fact the difference between this sequence and more standard replies is pretty big. I think it is worth playing around with this position a bit to appreciate the value of .
Black hasn't to worry as well as he is out in the safe and white has to take care of her single stone.