If your Chevy truck has a block heater: Plugging it in will preheat the engine coolant, making starting easier and potentially reducing wear and tear on the engine and battery in extremely cold weather. This is particularly helpful in sub-zero temperatures.
If your Chevy truck does NOT have a block heater: Plugging it in would do nothing. There's no system to receive the electricity.
To know if your truck has a block heater, check your owner's manual or look for a cord (usually around the front grille area or near the engine block) that can be plugged into an electrical outlet.