Final answer:
The termination of a contract between a seller and a broker after successfully closing a sale is known as performance. This indicates that all the duties stipulated in the contract were fulfilled, thereby terminating the contract.
Step-by-step explanation:
When a seller's broker successfully procures a buyer for the seller's property and the sale transaction is completed, the contract between the seller and the broker is terminated. This specific form of contract termination is referred to as performance. In real estate, performance is the fulfillment of the contractual duties, as agreed upon by both the seller and the broker. Once the sale closes and all obligations are met, the purpose of the contract is fulfilled, leading to its termination due to performance.