A Field Effect Transistor (FET) is a type of transistor that controls the flow of electrical current using an electric field. It consists of three main parts: the source, the drain, and the gate. The gate voltage influences the conductivity of a channel between the source and drain, allowing for efficient switching and amplification of signals. FETs are widely used in electronic devices due to their high input impedance and low power consumption. They come in various types, including MOSFETs (Metal-Oxide-Semiconductor FETs) and JFETs (Junction FETs), each suited for different applications in circuits and systems.