What kind of contract requires both parties to fulfill agreed-upon duties?

A bilateral contract is defined as an agreement between two parties where both parties make mutual promises to each other. Each party is obliged to fulfill their respective duties as stipulated in the contract. For instance, in a real estate context, when a buyer agrees to purchase a property and the seller agrees to sell it, both parties have specific responsibilities: the buyer must pay the purchase price, while the seller is expected to transfer ownership of the property.

This type of contract contrasts sharply with a unilateral contract, where one party makes a promise in exchange for an act from the other party, without any obligation for the other party to reciprocate. An executory contract refers to a contract that has not yet been fully performed by one or both parties, which doesn't specifically highlight the ongoing duties of each party in the same manner. Lastly, an implied contract is formed by the actions of the parties rather than written agreements, which tends to create obligations without explicit mutual promises.

In summary, a bilateral contract is fundamental in real estate transactions as it establishes clear expectations and obligations for both parties involved, ensuring that everyone knows their responsibilities in the fulfillment of the agreement.