makes an immediate eye while threatening to lasso tbe two white stones. protects from it, but is too slow for , which creates the other eye, and life with it. Noticing that also threatens the group, white presumably has to respond by connecting to her outside group with , thus ending this sequence in gote.
If white plays this way, puts the upper black stones in atari. Black must respond at . , in turn, threatens the group, so white must respond with . puts the entire black group in atari, so black must capture the entire invading white group with . In the sequence itself, white loses (and black gained) a lot more (locally) than he needed to.
So captures, but this is a capture two, recapture one, in which captures back the stone. Black is left with only one eye.