LTC4366HTS8-2 Documentation: What is Vth?

The datasheet contains a lot of equations.

Many of them referring to a parameter VTH.

I can guess it is some sort of Voltage Threshold, but I cannot find any explanation of exactly what it is referring to.

The closest I get is an example (pg16)  where it is set to 5V without any reference to what it is.

Please explain what VTH is referring to.

Best regards

Zippzapp