Screw is a more general term. The exact term should be bolts, screws, and nuts (screw caps). Bolts and screws are round and elongated objects with equal-spaced threads engraved on them. Bolts are flat-head cylindrical; screws are pointed at the front like nails. Bolts must be used together with screw caps, or used on objects that have been drilled with threads, and sometimes washers and spring washers are added. Screws are used for softer or thinner objects, and use their own thread while rotating while drilling forward. The thread on the bolt is relatively shallow without sharp edges; the thread on the screw is relatively sharp and deep, which is good for drilling into the object.