What exactly is silence?

Is it merely not having any auditory input? Because as an only child with parents who go to bed quite early, my life has had a lot of opportunity for that kind of silence.

Or is it a more profound kind of silence, with no input, no motion or restlessness, with focus? If that's the case, I rarely encounter silence, although often by my own action.

I find that I get a lot of quiet at night, by myself. I'm often up IMing with friends or reading things on the internet until late but when it's really, actually quiet and I'm not looking at a screen or chatting with anyone, I usually fantasize. It used to be general stories, sometimes super heroes or things from anime that inspired me, and I'd come up with characters and settings and try to come up with cool quirks. They rarely amounted to much. Since then I've actually channeled a lot of these kinds of fantasies into roleplaying with my friends. It's the quiet of the night that I come up with setting ideas, quirky NPCs, scenarios, combat encounters better than "you're in a square room with 4 goblins." I try to think of all the possible branches (there's never enough, they always undermine my original plans). I sometimes feel like my ideas don't translate as well into practice but I try to keep a log of them so that I can find ways to enact these (game)master plans when the mechanical part of my brain is turning.

Fantasizing about life things is also quite common. Running conversations with a friend, a boss, a girl, a fictional interviewer - I don't know whether these make me more or less anxious about these things but I guess it's how I do things.