1. Extracting heat energy from magma within the earth via steam turbines. This is what is mentioned in the article.
2. Using the ground as a sort of infinite thermodynamic reservoir via a heat pump working as the same principle as a refrigerator.
It's an umbrella term; it covers methods that leverage temperature differences between the ground and the air to exchange energy.
In FL, 64° aquifer water is used for cooling structures over 15k²ft. I worked on control systems for those.
~1c per 40m may not sound like much, but it quickly adds up over 50 years.
https://www.nytimes.com/2024/01/23/climate/geoexchange-clima... (may be paywalled)
"The system comprises an injection and production well pair drilled within a high-temperature, hard-rock geothermal formation. According to Fervo, the lateral sections of the wells were drilled leveraging technology innovations from the unconventional oil and gas industry with a 9 7/8-inch hole size, completed with 7-inch casing, and extended about 3,250 feet horizontally. They reach a maximum measured temperature of 376F (191C)."
https://www.powermag.com/innovative-enhanced-geothermal-syst...
Not sure where you're hearing the term "ground-source heat pump" in common usage, but it certainly has not filtered out into common parlance.