Geothermal, Greek Geo (land) and thermal (heat), is the science which studies the phenomena internal temperature of the earth and technology which aims to exploit it. By extension, geothermal is also the issue of geothermal energy of the Earth which is converted into heat.

There are three types of geothermal energy:

• geothermal little deep and low temperature,
• geothermal deep at high temperatures.
• geothermal very deep at high temperature.

These three types of geothermal heat levy contained in the soil.

Geothermal energy is used in networks of heating and hot water for thousands of years in China, in ancient Rome and the Mediterranean basin.

The increase in energy prices and the need to emit less greenhouse gas make it more attractive. In 2007, France's BRGM has with ADEME, created a Geothermal Department to promote, after endorsing various programmes of research, public service work. Two of its subsidiaries CFG Services (services and specialized engineering) and Geothermal Bouillante (which operates the power plant on Bouillante Guadeloupe) are involved in geothermal energy.