Why the second law of thermodynamics is called a directional law of nature?
In nature heat only moves naturally from warmer systems to cooler systems. One direction only. Never naturally from something cold into something hot.
We can pump heat out of a system by doing work on it, such as a refrigerator where the refrigerant is compressed - making it much hotter than the surroundings - then letting it give off heat to the surroundings, then expanding it across a valve where the evaporation and expansion causes it to get colder than the inside of the fridge - then allowing it to absorb heat from the inside of the fridge, then sending it back to the compressor to start all over again.