Commodities like oil and grain can be stored for later sale, affecting their prices. Frictions in the storage process can lead to times when storage operators don't sell in the market, causing price volatility. The option to delay selling stored commodities creates a convenience yield, which is like an extra profit for waiting. This yield reflects the future benefits of holding onto the commodity, not just immediate gains. When storage operators hold back from selling, prices become more unpredictable.