our trucks have a 110v plug in on the lower front cab, back of the fender, so when you pull up to your power pole, it's a short extension to hook up 110v power.
that is used to run the engine block heaters during the winter, and it extends 110v power to a couple outlets inside the cab.
Some are wired up to a trickle charger, that keeps the batteries topped off, as sub-zero temps will drain your battery's.
I found this article that has some good wiring info and diagrams on 12v wiring.
I like/need diagrams.
The Truck Electrical Center
it shows our block heater shore hookup.