What is a tool with jaws for tightening and loosening nuts?

A tool with jaws for tightening and loosening nuts is called a wrench. Wrenches come in various types, including adjustable wrenches, socket wrenches, and combination wrenches, each designed for specific applications. They are commonly used in mechanical and construction work to grip and turn fasteners securely. The adjustable wrench, in particular, features movable jaws to accommodate different sizes of nuts and bolts.