The transistor, a semiconductor device, is the device that made all our modern technology possible. It is used to control the current and even to amplify it based on an input voltage or current. There are two major types of transistors, the BJT and the FET. Under each major category, there are many subtypes. This is the most significant difference FET and MOSFET. FET stands for Field Effect Transistor and is a family of very different transistors that collectively rely on an electric field created by the voltage on the gate in order to control the current flow between the drain and the source. One of the many types of FET is the Metal-Oxide Semiconductor Field Effect Transistor or MOSFET. The Metal-Oxide Semiconductor is used as an insulating layer between the gate and the substrate of the transistor.
The oxide insulation in most MOSFETs nowadays is Silicon Dioxide. It might seem confusing as silicon is not a metal but a metalloid. Initially, a metal was actually used but has been replaced with Silicon due to its superior characteristics. The Silicon Dioxide is basically a capacitor that holds charge whenever voltage is applied to the gate. This charge then creates a field by pulling oppositely charged particles or repelling particles with the same charge and allows or restricts the flow of the current between the drain and source.
Although there are a wide number of transistors that can be used in digital circuitry, it is the MOSFET that is currently preferred. CMOS (Complementary Metal-Oxide Semiconductor) basically uses a p-type and n-type MOSFETs in pairs to complement each other. In this configuration, MOSFETS only have significant power consumption during switching and not while it holds its state. This is very desirable, especially in modern computing equipment where power and thermal limits are pushed to the edge. Other types of FET cannot replicate this capability or are too expensive to manufacture.
@Kate (thumbs up) has given a complete answer. The difference between FET and MOSFET is the MOS, i.e. Metal Oxide Semiconductor. Metal is the metal terminal for the Gate. Oxide is silicon oxide used as insulator. Semiconductor is the PNP or NPN material below forming the Field Effect Transistor or FET.
As Kate stated, the depletion is created by capacitative effect across the gate and insulator. When in enhanced state, a channel forms in the semiconductor to allow large current to flow.
JFETs are depletion mode devices and reducing Vgs reduces the drain current. Most MOSFETs are enhancement mode devices, but some of them are depletion mode. A depletion mode MOSFET behaves like a JFET.
They are not the same, MOS-FET was invent after FET. It has better quality than FET like spending less power and faster.
