The world needs a new source of energy, an unspillable source.

Give me a desicrition of geothermal energy, please. If anyone can at all?

All I need to know is if geothermal energy is a nonrenewable resource or a renewable resource. I also need some illustrations on how the energy resource is used (just give me a link to that). I also need to know its advantages of its use and its disadvantages. Thanks for your answer. You have all my gratitude for it.