A screw is a type of fastener that is used to hold two or more objects together. It consists of a cylindrical shaft with a helical groove, or thread, on its surface. A screw is inserted into a pre-drilled hole and turned, causing the threads to bite into the material and hold the objects together.
A machine screw is a type of screw that is designed to be used with a nut, or in a tapped hole. It is typically smaller in diameter than a regular screw and has a finer thread. Machine screws are used to hold machine parts together and are typically made of a stronger material, such as steel or brass, than regular screws. They are also usually more precise in their dimensions and tolerances.