NUT (noun) a small (usually square or hexagonal) metal block with internal screw thread to be fitted onto a bolt.
BOLT (noun) A fastener consisting of a threaded pin or rod with a head at one end, designed to be inserted through holes in assembled parts and secured by a mated nut that is tightened by applying torque.
Nuts and bolts are common fasteners for chair and table legs, for instance, and for connecting metal parts. With extremely few exceptions (electric fan blades are one), they all are tightened by turning the nut to the right (clockwise) and loosened by turning it in the opposite direction. This is very easy for most people to remember.