This is the renewable light or heat that comes from the sun. There are two basic ways to use solar energy. To heat things, (eg houses, water, food, etc...) known as solar thermal energy. And also to turn the light from the sun directly into electricity using solar panels.
However, solar energy is still more expensive than if you produce it through the burning of coal.
It is clean, doesn't pollute the air, land or water and there is plenty of it! Making it 'renewable'. If we were to use more solar energy we can save our fossil fuels like coal, oil and natural gas.