Solar energy, or energy from the sun, travels down to the earth in rays. Some rays we can see, and others we can't. We get most of our energy from the sun because it comes down in large amounts every day. However, only a small fraction of that energy reaches earth; most is sent into space. Solar energy is a renewable resource because the sun is always there, and always producing heat for us to do things, such as drying our clothes or boiling water.
Electricity can be generated by using the wind. You can see this happening at wind farms. The blades, designed like airplane wings, turn to create power. Some parts of the globe rely on wind to pump water. It is used to plant crops, sail ships or to provide water to remote places. It is clean and free, but can be difficult to harvest on days that have little or no wind.
Water is similar to the wind; it is produced by the earth and nearly impossible to run out of. Flowing water and waves from the ocean have been used to power wheels or run mechanical equipment, and more recently used to create energy. Water can be trapped in dams to supply generators because of tides and currents.
Biomass is material that can be used to create fuel. This material can be many different things, including living or dead plants and tree branches, yard clippings, wood chips and animal waste. Those substances can create fuel because of the energy stored inside of the decaying matter, which produces carbon dioxide.