Solar energy, the earth’s primary source of energy
Most of the earth’s energy comes from the sun. That is true for fossil fuels such as coal, oil, and natural gas. Prehistoric plants stored the Sun's energy in their leaves, and when they died and eventually formed energy seams. So when we burn fossil fuels, we're releasing chemical energy that was stored in plants millions of years ago.

The same goes for wind. Warm air tends to rise, and winds are due to other air moving in to replace it. Winds and thermal heating from the sun drive the ocean’s currents as well (as well as the gravitational pull from the moon's rotation - a source of kinetic energy). Hydropower is only available because solar heating evaporated water which provided the precipitation by which the water for the hydropower became available.

Sources such as biomass, ethanol, vegetable oils, and other plant based energy sources also are available only by the energy conversion provided through plants by sunlight.

The energy from Stars like our Sun generate their power by turning mass into energy through the process of nuclear fusion. Essentially, hydrogen is converted into helium in the Sun's core, and a little bit of energy is produced every time the reaction occurs.

Nuclear energy – another energy source for the earth.
The sun’s energy is derived from a nuclear fusion source and provides most of the energy sources used on the earth. However, Nuclear energy produced on or within the earth provides an exception to the energy sources supplied by the sun. These sources are not hydrogen based (hydrogen bombs are an exception).  The earth's nuclear energy sources are typically derived from a nuclear reaction from a fissionable radioactive material. Nuclear power plants use these fissionable nuclear materials for their energy sources.