Depletion mode:
In depletion mode, the transistor is normally ON, meaning that there is a conducting channel between the source and drain terminals even when no voltage is applied to the gate terminal. To turn off the transistor, a negative voltage is applied to the gate terminal to deplete the channel.

Source and Drain Connection:
In depletion mode, the source and drain terminals are connected by a conducting channel. This conducting channel is formed by the presence of free charge carriers in the channel region of the transistor.

Insulating Channel:
An insulating channel refers to a channel that does not allow the flow of charge carriers. In a depletion mode transistor, the channel is not insulating.

Conducting Channel:
A conducting channel refers to a channel that allows the flow of charge carriers. In a depletion mode transistor, the channel is conducting.

Vddd and Vss:
Vddd and Vss are commonly used terminology in integrated circuit (IC) design. Vddd refers to the positive supply voltage, while Vss refers to the negative supply voltage or ground. These terminologies are not directly related to the connection between the source and drain terminals in a depletion mode transistor.

Conclusion:
In depletion mode, the source and drain terminals are connected by a conducting channel. This conducting channel allows the flow of charge carriers even when no voltage is applied to the gate terminal.