Final answer:
A written agreement where a buyer agrees to buy and a seller agrees to sell is called a contract, which includes terms like warranties and service contracts especially for large purchases.
Step-by-step explanation:
A written agreement in which a purchaser agrees to buy and a seller agrees to sell is known as a contract. This contract specifies the terms and conditions of the sale, and upon signing, it becomes a legally binding document that holds both parties to their responsibilities. For example, the seller may provide certain guarantees about the product's quality or functionality, often referred to as a warranty.
Moreover, the seller could give the buyer the option to purchase a service contract. In such a service contract, the buyer pays an additional fee, and the seller commits to repairing or addressing any issues that arise with the product within a specified period post-sale. This type of service contract is especially prevalent in transactions involving sizeable investments such as automobiles, home appliances, or real estate.