There are lots of heat pumps out there.
You can get ductless or geothermal heat pumps.
They can be ground source or air source heat pumps. Also, the way the device is installed is vastly different. Just for a geothermal heat pump, the installation can be done in four ways. Three of them are open loop systems. For geothermal heat pumps, the outdoor unit needs to be buried under the ground. The idea behind this is that the ground temperature is way better than the air. In the winter it is warmer underground and vice versa with summer cooling. The open loop system is buried in the backyard either horizontal, vertical or lake/pond style. The horizontal loop system has two pieces of piping buried side by side and different depths like four feet or 6 feet in a large trench in the backyard. This is typically the method used for residential homeowners. The space is there and the home can take the lawn being ripped up. The vertical loop system has holes drilled into the ground and piping pushed down into the holes to create a U shaped loop system. This is minimally invasive and doesn’t take quite as much space. That is why it is used for commercial HVAC. Larger companies and schools tend to rely on the vertical loop. The lake/pond style has the piping in the water to utilize that source. The final installation method is a closed loop system that can be near another body of water or use a well. Basically the system needs clean, reliable water in order to provide heating and cooling to the home.