Simply put, geothermal energy is heat generated and stored in the Earth.
The heat is pumped out from a layer of earth just below the crust, and used as home heat or for industrial applications like electricity generation.
Nations around the planet are starting to research how geothermal energy can work for them.
One of the most notable of these nations has to be Iceland.
In January, the nation's Parliament gave the green light for more than a dozen new alternative energy projects, including 11 geothermal power stations.
In Iceland, geothermal energy heats houses, powers industry and ensures gushing hot water fills bathtubs and thermal spas year round.
If you want to know the answer to what is geothermal energy, then Iceland is the best example to look at it.
Iceland only uses about 17 percent of its electricity to power homes and domestic industry, which keeps energy prices extremely low.
Which leads to a surplus of power they can sale to other nations.
Iceland's leaders are now considering connecting the country's electricity grid with continental Europe, using up to 1,200 miles of undersea cable.
The Iceland power company, Landsvirkjun, has shared details for the proposed cable-connection project.
The massive submarine interconnector would first extend 700 miles to the north of Scotland and then to continental Europe, another 500 miles away.
Upon completion, the cable connection would be three times longer than the existing link between Norway and the Netherlands, currently the world’s longest.
And this is all part of a global move towards geothermal energy.
A recent report by Pike Research showed that geothermal development has expanded from 26 countries in 2010 to 64 at the start of this year, with 567 geothermal projects underway worldwide.
For right now though, Iceland is hogging the global geothermal spotlight.
According to Invest in Iceland project manager Kristinn Haflidason:
"Iceland's geothermal infrastructure is highly reliable. It's also more than just electricity... a geothermal power plant produces steam, hot water and cold water.
That's ideal for green projects with high energy needs, such as building data centers, industrial scale greenhouses and fish farms."