Junction Field Effect Transistor
The JFEt Transistor is very similar to a regular transistor as far as hooking it up goes.  Common Emitter = Common Source Configuration. 
The Main difference in operation Of a JFET to a transistor, The transistor relies on current to operate the base while the JFET gate is controlled by voltage.
As someone above stated it is very similar to a tube amplifier but with much less voltage on the Drain. What is it good for, inputs that have very little current but have voltage. I have used it for timing circuits, charging a capacitor and resistor combination, since the gate does not draw much current, the gate will not bleed down the voltage on the capacitor as it charges. 555 Use FETs  It has and may still to used in Tuner RF stages as it will not overload with a large signal as a transistor would, acting as a diode detector and let the signal from a strong station override a more distant station. If you want to design something I would use a MOSFET instead, VN2222 is a low level N channel. More commonly used today. Same principle