A put-call spread is a strategy used in option trading that involves purchasing a put option and selling a call option on the same underlying asset, with the same expiration date. The put option gives the holder the right, but not the obligation, to sell the underlying asset at a specified price (the strike price) on or before the expiration date. The call option gives the holder the right, but not the obligation, to buy the underlying asset at the strike price on or before the expiration date.

In a put-call spread, the trader will typically purchase a put option with a lower strike price and sell a call option with a higher strike price. This creates a net credit, as the premium received from selling the call option is typically greater than the premium paid for the put option. The trader is hoping to profit from the difference between the two premiums, as long as the underlying asset stays within a certain price range.

The put-call spread can be used as a way to hedge against potential losses in the underlying asset, or as a way to profit from neutral or mildly bullish market conditions. It's important to note that the put-call spread involves taking on both long and short positions, so it is important to understand the risks and potential rewards before implementing this strategy.