Two-phase locking (2PL) is a concurrency control mechanism used in database management systems to ensure that transactions are executed in a safe and consistent manner. It operates in two distinct phases: the growing phase, where a transaction can acquire locks but cannot release them, and the shrinking phase, where it can release locks but cannot acquire any new ones. This structure helps prevent issues like deadlocks and ensures that transactions are isolated from one another. The primary goal of two-phase locking is to maintain the ACID properties of transactions, particularly atomicity and isolation. By enforcing a strict order of lock acquisition and release, 2PL helps to avoid conflicts that could lead to inconsistent data states. However, while it provides strong guarantees, it can also lead to reduced concurrency and potential performance bottlenecks in high-transaction environments.