Unilateral trading is speculative trading. Judge whether the market will go up or down in the future, and then buy up or buy down. If you judge correctly, you will make money; if you judge wrongly, you will lose money. The risk is relatively high and the expected return is relatively high.

Arbitrage trading is divided into inter-period, inter-market and inter-variety, that is, there should be a stable difference between different contracts with correlation. If the price difference deviates, you can open two contracts at the same time, with the same trading volume and opposite directions, so as to obtain stable income. For example, the price of silver 140 1 contract and silver 1406 contract should be maintained at around 70 points. On Monday, due to market fluctuation, the contract of 1406 was 90 points higher than the contract of 140 1, so you can short 1406, go long 140 1 at the same time, and close your position while the spread is restored to 70 points. Then What we are mainly studying here is arbitrage trading.