A water/water heat pump is absolutely not the same thing the other commenters are talking about. They're mostly talking about an air/air heat pump, where it's literally all the same parts but has a reversing valve so it can either be hot/cold or cold/hot among the coils with fans blowing through them.

This is more like what they're talking about, but they do come in a lot of shapes and sizes and can be more or less integrated into central systems.

https://senville.com/mini-split-heat-pumps/