The buyer, seller and intermediary agency belong to an intermediary contract relationship. An intermediary contract refers to a contract in which the parties agree that one party will accept the entrustment of the other party and, in accordance with the other party's instructions and requirements, report to the other party the opportunity to conclude a contract or provide intermediary services for the contract, and the principal will pay remuneration. In an intermediary contract, the party who accepts the commission to report the opportunity to conclude a contract or provides the transaction medium is the intermediary, and the party who pays the remuneration is the principal. Article 961 of the Civil Code states that an intermediary contract is a contract in which the intermediary reports to the client the opportunity to conclude a contract or provides intermediary services for concluding a contract, and the client pays remuneration.