A ratchet wrench is a hand tool used for tightening or loosening fasteners, such as nuts and bolts. It features a mechanism that allows the user to turn the tool in one direction while the socket remains stationary in the opposite direction. This design makes it easier to work in tight spaces where a full rotation of the wrench is not possible. The ratchet mechanism consists of a gear and a pawl, which engages and disengages as the handle is turned. Commonly used in automotive and construction applications, a ratchet wrench often comes with interchangeable sockets to fit various sizes of fasteners, enhancing its versatility and efficiency.