What type of contract exists when one party agrees to provide a service without a promise of compensation from the other party?

A unilateral contract is a type of agreement where one party makes a promise in exchange for an act or service performed by the other party, without any obligation on the other party to carry out the action. This means that only one side—the offeror—bears the responsibility to fulfill the terms of the contract, while the other party—the offeree—can choose to perform the service without any guarantee of compensation or a reciprocal promise.

In real estate or other service industries, an example of a unilateral contract would be a reward for finding a lost pet. If someone advertises a reward for the return of their pet, they are making a unilateral offer; the person finding and returning the pet does not owe anything back to the pet owner unless they choose to return the pet, at which point the owner must fulfill their promise of payment.

Bilateral contracts, in contrast, involve mutual promises where both parties have obligations to perform certain actions or services. Conditional and contingent contracts relate to specific conditions that need to be met for the contract to be enforceable or valid, which does not accurately reflect the nature of the service agreement described in this question. Therefore, a unilateral contract best fits the scenario where one party provides a service without a promise of compensation from the other