When a professional equity options trader is forced to buy back a short stock position (called a Buy-In) that hedges a long delta options position and the stock opens higher the next day.
You go out short 10000 shares of EET against a long 10000 delta options position. Overnight you are forced to buy back your shares at $40. The next day the stock opens at $42. You have just made $20000, hence the term Buy-Win.