Delta refers to the first derivative of the option price relative to the target price (that is, the target price changes 1 unit, and how much the option price changes). Delta exposure means that the options held are not hedged. ) lost Delta. For example, the Delta of an option portfolio is 500, and the Delta exposure of this portfolio is 500, without any Delta hedging. There are many reasons for the change of Delta exposure, which may be that the portfolio itself has changed, such as buying or selling options. Besides, it is caused by gamma rays. Gamma is the second derivative of the option price relative to the target price (that is, the target price changes 1 unit, and how much Delta changes). If the Gamma of the portfolio is not zero, the Delta exposure of the portfolio will also change when the price of the subject matter changes.