Geothermal power is based on a heat engine: a machine which produces usable energy (e.g. electricity) out of the transfer of heat from a high-temperature heat source to a low-temperature heat sink (a process which would happen naturally, given a transfer process).

A ground-source heat pump is a heat pump: a machine which consumes usable energy in order to move heat from a LOW-temperature heat source to a HIGH-temperature heat sink (a process which would not occur naturally without energy input due to the 2nd law of thermodynamics).