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.