Cash futures arbitrage is a trading strategy that involves buying an asset in the cash market and simultaneously selling the same asset in the futures market to profit from price differences between the two markets. This strategy is based on the idea that the price of an asset in the cash market and the futures market should be equivalent, adjusted for the cost of carrying the asset until the futures contract expires.

Here's how it works:

1. Identify a price discrepancy between the cash market and the futures market.

2. Buy the asset in the cash market at the lower price.

3. Sell the same asset in the futures market at the higher price.

4. Hold the position until the futures contract expires.

5. Close the position by selling the asset in the cash market and buying it back in the futures market.

The profit is the difference between the sale price in the futures market and the purchase price in the cash market, minus the cost of carrying the asset (such as interest, storage, and insurance).

Cash futures arbitrage is a low-risk strategy that can be used to earn a risk-free profit, but it requires a high degree of market efficiency and liquidity.