The picture comes from the internet.
There is no notary, the conditions are incomplete and the information is not equal. For example, I don't know the quality of soybean in the above example, so I gradually evolved into a formal contract, which is a futures contract. Futures contract refers to the standardized contract formulated by the futures exchange, which stipulates to deliver a certain quantity and quality of the subject matter at a specific time and place in the future.
According to the terms stipulated by the exchange, both parties are fair. Investors in need can purchase contracts directly on the exchange. The act of buying a contract is called opening a position. After buying, they can close their positions by physical delivery. In the above example, they can also sell the contract to get the difference. For example, after 1 month, my tofu shop closed down and this batch of soybeans was not needed, so I discussed with my boss to sell the opposite list. This is called hedging and closing futures.
At present, the market is mostly speculators, that is, hedging transactions.
If you don't know the basic knowledge of futures, you can also ask me. The low commission account opening process is private.