Basically a shunt trip CB is...
A device (CB) that can be "shut off" from a remote location.
The CB has a coil or solenoid installed that will shut the CB "off" when power is applied to the coil or solenoid. THis option is usually factory installed, but is a field installable item on some large frame (amperage) CB's.
The control voltage can range from 12 volts to 480 volts normally.
There are numerous uses for ST CB's, computer/data rooms, gas stations, elevators, cooking equipment, etc.