The word solar stems from the Roman word for the god of the sun, Sol.  Therefore, the word solar refers to the Sun and “solar power” is power from the Sun.

When we say something is solar powered, we mean that the energy it uses for power came directly from solar energy or sunlight energy.  The sun provides Earth with 2 major forms of energy, heat and light.  Some solar powered systems utilize the heat energy for heating while others transform the light energy into electrical energy (electricity).

There are many practical applications for solar power that are in use today.  Passive solar home designs utilize heat energy.  By slanting windows in a house and facing them to the south you can control the heat energy that enters the house.  During the winter when the Sun is low in the sky it shines into the window to warm and illuminate the house.  During the summer when the Sun is high in the sky the slant of the windows keeps the sunshine out so that the house stays cooler.

There are vehicles that run on solar power.  Some have PV panels as a direct power source that convert light energy into electricity to power their motors.  Since those cars will not run when the sun is not available it is more practical to have a car powered by batteries that can be recharged with solar energy.

In countries and locations where traditional power sources are not available it is more economical to power a house with solar energy.  To these people, solar is not an alternative energy; it is their primary energy source.

(Source:http://www.makeitsolar.com/solar-energy-information/03-solar-power.htm)