A more thorough explanation:

Definition: A mistake is an error or misconception. In contract law, it refers to a situation where the parties did not mean the same thing when they agreed to a term or provision. It can also occur when at least one party held a belief that was factually or legally false. This can result in the contract being subject to modification or rescission. In criminal law, a defense that claims either a misconception of the law or some fact. The defense of mistaking the law almost never succeeds. Mistakes of fact can work as a defense more often, especially if they are reasonable.

• Contract Law: If a person agrees to sell a car, but the buyer thinks they are buying a truck, there is a mistake in the contract. The contract may need to be changed or canceled.
• Criminal Law: If a person is accused of stealing a car, but they thought it was their own car, they may have a defense of mistake of fact.

These examples illustrate how a mistake can occur in different areas of law. In contract law, a mistake can happen when the parties have different understandings of what they are agreeing to. In criminal law, a mistake can be a defense if the person did not have the knowledge or intent to commit a crime.