A natural key is a type of unique identifier used in databases that is derived from the actual data itself. Unlike artificial keys, which are created specifically for database purposes, natural keys are based on real-world attributes that can uniquely identify a record. For example, a person's Social Security Number or an ISBN for a book can serve as natural keys. Using natural keys can simplify data management since they often have inherent meaning. However, they can also pose challenges, such as changes in the real-world data or privacy concerns. Therefore, careful consideration is needed when choosing natural keys for a database.