Unconsciousness is a state of being unaware of what's going on around you, either because you're not awake or because you're simply oblivious. If you fall asleep during a movie, and your unconsciousness means you'll miss the ending.
Even if everyone in your family is mad at each other, your little cousin's unconsciousness of the argument might make it easier to have a peaceful Thanksgiving. And after the meal, the great quantities of food eaten may result in the unconsciousness of half the guests, who doze in the living room, snoring softly. In both kinds of unconsciousness, someone isn't conscious, or aware, of their surroundings.