1. There are two lines parallel to the S pole (source) opposite to the D (drain), and the center is the G pole (gate) 2. Two functions, switch (basically no voltage drop in saturated state), isolation
( Using a diode)
3. The off condition GV<DV, the flow direction in the state is the direction of the diode, the turn-on condition GV is greater than DV, the state flows in the opposite direction of the diode
Reference:
MOSFET Turn-on Conditions