A type of screwdriver, also known as a flathead screwdriver. It is a screwdriver with the business end being flattened and thin, much like a small chisel. It is designed to work with a screw that has had a single groove, or slot, cut into it.
Slotted screwdrivers are probably the oldest kind still in use due to the ease in which a slotted screw can be made and that slotted screwdrivers are also useful for prying, splitting, scraping and gouging.