God's first act in preparing the earth for life was to create light.
And God said, 'Let there be light,' and there was light. God saw that the light was good, and he separated the light from the darkness. – Genesis 1:3-4
The qualities of light operate in both physical AND spiritual realms.
Even though light is a common part of our every-day existence, there are no words to adequately describe it. It is the prerequisite for all life. The best way to understand light is to think about what it does.