system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly is sous-vide? Isn't it just boiling the food?
gpt
Here's how it works. You wrap your food in plastic and put it in a water bath set to a precise temperature. It turns out that for protein foods, it's not how long they cook that determines how done they are, but the maximum temperature reached. So sous-vide lets you control precisely whether a steak is rare, medium, or wherever *exactly* you want it.

If you want a medium rare steak, put it in water at 130F. After an hour or so that temperature will be reached all through the steak, but you can leave it in for another hour if you want and it barely changes. This makes it very flexible for cooking when you aren't quite sure when you will be serving dinner.