The field effect transistor is a component that uses only one junction instead of two as in bipolar transistors. Even though it is only one junction that also functions like a diode, the actual layout of the materials make it have some properties that allow a single junction device function like a transistor.
The layout of the FET is a bar of semiconductor material that has a ring of an oppositely doped semiconductor material around it. This Transistor is called the junction field effect transistor or JFET.
There are two types of JFET, called N-channel and P-channel. The name comes from the type of material that makes up the bar of material, for example the N-channel is a bar of N material with a ring of P material around it.
The explanations here are given for P-channel JFETs, as with bipolar transistors, just reverse polarities for N-channel JFETs.
Similar to the Bipolar transistors, FETs have three terminals, Source, Gate and Sink that correspond in function to the Collector, Base and Emitter of the BJT, respectively