Wood screws are probably the most commonly-used mechanical woodworking fasteners.
Wood screws have a smooth shank that allows the screw to pull the two pieces of wood together for a tight joint. Wood screws also taper along the threaded portion optimizing the screws holding power in wood. This is why some people use special tapered drill bits for pilot holes. They can also be used to attach hinges, hardware, locks and other non-wood objects.
While all wood screws have an aggressive thread for grabbing and holding the wood, there are many differences in the varieties of wood screws, based upon the gauge, length, head type and drive type of the screw in question. The threads are usually coarse and deep to help them grab the wood.
Wood screws are usually made of hardened steel, but are often found in brass and stainless steel.