Regular heat pumps with a fan condenser are called air source heat pumps. This ground source heat pump instead uses a flexible pipe buried a hundred or more feet in the ground inside of a bore hole. This is more efficient than the air source heat pumps – the electricity cost is lower. This kind of heat pump is uncommon in the US but is common in Europe.
https://www.local10.com/business/2023/07/13/little-known-but-efficient-a-different-way-to-heat-and-cool-your-house/
