A Knock-Out (KO) is an option that automatically expires worthless if the underlying asset reaches a certain price level. It is also known as a barrier option. A Knock-In (KI) option, on the other hand, only becomes active if the underlying asset reaches a certain price level. Knock-In options are generally less common than Knock-Out options. Both types of options are used for hedging and speculative purposes, and their pricing depends on a variety of factors, including the underlying asset price, the option’s strike price, the option’s expiration date, and market volatility.