What do you think about?

That sounds like a vague question, but it's really not - I mean it entirely as how it is. As in, at times when you're not doing something that requires full attention, what exactly goes on in your head? Say, you're walking somewhere, or maybe doing housework. Even if you're listening to music, you've got to be thinking about or imagining things, right? Or not? Do you just kind of picture the band playing? Idk. Do you just think about things that have happened / are going to happen in your day? That can't be stretched out enough, surely? Do you imagine things with people you know irl? I can't remember how I thought before I got into fandom stuff (loooooooong time ago) and it's really intriguing me ~ ahhhh curious...