This video on "Know-How" series helps you to understand the different modes of operation of MOS Transistor. The structure of simple nMOS is shown and voltage conditions are varied
to depict the accumulation, depletion and inversion modes.

The video link of MOSFET Types, Symbols and it's Significance | Applications is shared below:
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TimeCodes:
Introduction to NMOS Transistor: (00:00)
Threshold Voltage: (04:18)
Accumulation Mode: (05:47)
Depletion Mode: (07:17)
Inversion Mode: (08:34)