This type of strategy (buying one option and selling another with a higher strike price) is known as a credit spread because the amount received by selling the put option with a higher strike is more than enough to cover the cost of purchasing the put with the lower strike. The maximum possible profit using this strategy is equal to the difference between the amount received from the short put and the amount used to pay for the long put. The maximum loss a trader can incur when using this strategy is equal to the difference between the strike prices and the net credit received. Bull put spreads can be created with in-the-money or out-of-the-money put options, all with the same expiration date.
Investment dictionary. Academic. 2012.