What is nothing?

This might be too vague for a proper philosophy discussion but I don't see it being a great fit anywhere else. It's an old question that has been discussed a thousand times before I'm sure but it's something that's been on my mind a lot lately. I guess it's a spin on the classic "what existed before time began"<br><br>What is the meaning of nothing? What is nothing made of? Is nothing physically possible? Is it the absence of all matter, space, time? <br><br>I don't know if it's just my brain's inability to look past the present moment, but the idea of nothing seems impossible to imagine. The closest I can come to imagining true nothingness is the absence of my own consciousness, the feeling of being asleep when I have no dreams. And even that doesn't seem "nothing" because I don't know what's happening while I'm asleep. The only way I'm able to picture nothing is waking up from that nothingness and remembering a life I had before.