Screws can be broken down into three main categories:
Wood screws
Wood screws are designed for use in hard and softwood, MDF and chipboard. They have a tapered body, coarse threads and a sharp tip.
Machine screws
Machine screws are used for metal working and are designed to be inserted into a tapped hole or tightened with a nut. They usually have a straight body and a flat tip.
Speciality screws
There are many different types of speciality screws for applications such as drywall, decking, masonry, and ceramic.