Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) are classified into different types based on their structures and operating mechanisms. The main categories of MOSFETs include Enhancement-mode MOSFETs, Depletion-mode MOSFETs, and Power MOSFETs.

1. Enhancement-mode MOSFETs: These types of MOSFETs are normally off devices, requiring a positive voltage at the gate terminal to create a conducting channel between the source and drain terminals. They are widely used in digital circuits such as logic gates and amplifiers due to their low leakage current and low power consumption.

2. Depletion-mode MOSFETs: Unlike enhancement-mode MOSFETs, depletion-mode MOSFETs are normally on devices, meaning they conduct current without the application of any gate voltage. They require a negative voltage at the gate terminal to turn them off. Depletion-mode MOSFETs are commonly used in applications where the transistor needs to be normally conducting and turned off by applying a voltage.

3. Power MOSFETs: Power MOSFETs are designed to handle high voltage and current levels, making them suitable for power switching applications such as motor control, power supplies, and inverters. They are characterized by their low on-resistance, high breakdown voltage, and fast switching speeds. Power MOSFETs are available in various configurations, including N-channel and P-channel types.

The specific differences between these types of MOSFETs lie in their threshold voltages, operating characteristics, and applications. Enhancement-mode MOSFETs require a positive voltage to turn on, while depletion-mode MOSFETs require a negative voltage. Power MOSFETs, on the other hand, are optimized for high power applications and feature lower on-resistance to minimize power losses.

In summary, MOSFETs are classified into different categories based on their operating modes and structures, each offering unique advantages for specific applications. Understanding the differences between these types of MOSFETs is essential for selecting the right transistor for a given electronics design.