What is the VT in MOSFET

[datnt]

what is the VT ? What things VT depend on?
in the VLSI book. they write:

Qchannel = CV
• V = Vgc – Vt = (Vgs – Vds/2) – Vt

But i don't know what is the Vt? any help would be appreciated..

 

[crutschow]

Vt is the gate-source threshold voltage, at which point the MOSFET just starts to conduct.
It's value depends upon the MOSFET design and also varies significantly between different units of the same type.