"Testify" is a term commonly used in legal contexts, referring to the act of giving evidence or making a statement under oath in a court of law. When a witness testifies, they provide information about what they know regarding a case, which can help the judge or jury make informed decisions. In a broader sense, "testify" can also mean to express or affirm something based on personal experience or belief. For example, someone might testify about the benefits of a product or service, sharing their positive experiences to support its value.