What is a winter plug for on a husky 55 chainsaw?

It is device so that warm engine heated air can sucked into the air cleaner to prevent carburetor icing. Normally air cleaners suck air from the outside without it first going across the engine.
 
If you ever used a snowblower they use intake systems that draw air over the exhaust and/or engine to warm the carburetor.
 
I have seen riding mowers that need a way to heat the air entering the carburetor so the carburetor doesn't ice over.

Actually there is two devices. One for 0 C temps located in the air filter box and one additional cover for - 5 C temps.
 
Here is a screen shot from the owners manual.

Papa Tom
Thank you for the quick response! I learned something new in my old age! I guess I missed that in the manual.😬

Just proves you are still alive. None of is ever too old to learn something new. I'm past 60 now and still learning new things.
 
Also no question is dumb or stupid if you truly don't know the answer and need to know. The only dumb question is the one not asked.