Solar4Scholars: Solar Energy
There are two ways that "solar energy" is understood.
One way is called solar thermal, and in this the sun is used to heat water.
This is used in two different ways - directly, to heat water, and indirectly, through the use of a closed loop system, with glycol.
Read about solar thermal.
Another is called solar photovoltaics. This is becoming more popular all the time. In this, light from the sun is used to begin an electrical current.
Read about solar photovoltaics.