Directly or indirectly, virtually all energy we use is derived from solar energy: wind is created when solar energy creates differences of temperature on areas of the earth's surface, biomass energy is derived from solar energy that has been captured and stored, and fossil fuels are derived from biomass that has been trapped and transformed by geologic processes over millions of years.
In addition to the many indirect ways we use the sun's energy, there are three main ways that we use solar energy directly:
Passive solar is when buildings directly take advantage of solar energy. A greenhouse is an example of passive-solar structure. While virtually all structures capture passive solar energy to some extent, sophisticated passive solar buildings are precisely designed (using window placement, building orientation and shape, thermal mass, etc) to take maximum advantage of solar energy during the course of the year.
Solar thermal systems actively collect, transport, and utilize solar energy to generate heat. The most common systems are those used to heat water, but there are also systems designed for other applications like space heating and cooking.
There are two primary solar-electric technologies, photovoltaics and concentrating-collector systems: