A geothermal resource is one that is accessible. A geothermal resource constitutes quantity of stored energy between the earth surface and specific depth in the earth’s crust underneath a specified area and is measured from local mean temperature. The most common criteria to classify geothermal resources is the enthalpy of geothermal fluids which is the energy carrier. It is the enthalpy that influences or determines the classification of the geothermal resource as low enthalpy, medium enthalpy, or high enthalpy geothermal resource. Geothermal sysems can be classified as convective dominated systems, which include liquid-vapour dominated hydrothermal system, conductive dominated system which include hot rock and hybrid systems which source from convection, conductio and high heat producing source e.g. magma. A geothermal system is made up of three main elements namely, a heat source, a reservoir, and a fluid, which is the carrier of the heat. The heat source can be either a very high-temperature (greater than 600 °C) magmatic intrusion that has reached relatively shallow depths (5 to 10 km) or, as in certain low-temperature systems. Most geothermal resources are near the boundaries of the earth's tectonic plates. The most active geothermal resources are usually found along major tectonic plate boundaries where most volcanoes are located.