Physics for DUmmies:
What is Thermodynamics?
Thermodynamics is the way a Thermos works.
How does the Thermos know whether the hot stuff should be kept hot or the cold stuff should be kept cold? Through "thermodynamics".
You see, food and coffee and stuff has these units of heatedness. They are called "British Thermos Units", because a British guy invented them. When your food has positive BTUs, then the Thermos figures out to keep it hot. When your food has negative BTUs, the Thermos keeps it cold.
It's like magic, except kinda more scientific. And that's all I'm gonna say about that.