When you sell a naked put option one of the following three situations will take place:

1. The price of the underlying stock falls below the strike price of the option. Then the option will be exercised and the seller of the option must purchase 100 shares of the underlying stock at the strike price.

2. The stock stays above the strike price of the sold put option and the option expires. The seller keeps the premium collected at the time of the sale.

3. The seller of the put option may buy back the option before any of the above scenarios take place.