A field-effect transistor (FET) is a type of semiconductor device that controls the flow of electrical current. It operates by using an electric field to influence the conductivity of a channel made from semiconductor material. FETs are widely used in electronic circuits for switching and amplifying signals. There are several types of FETs, including the MOSFET (metal-oxide-semiconductor FET) and the JFET (junction FET). These devices are essential components in modern electronics, found in applications ranging from computers to mobile phones. Their ability to efficiently control current makes them crucial for various technologies.