What Is This Fancy-Looking Coil Of Copper?

What is this fancy-looking coil of copper? It is meant to recover the heat from your drain before sending the water to your hot water tank and is also code in Manitoba when it comes to new builds.

Most people don't seem too impressed and I would love to know the numbers on how it contributes to us being more efficient, but either way, it is always a fun conversation to have and learn more about new homes.