Why do we sometimes see light during meditation?.

Question:

“I’m looking for information regarding an “episode” I had the other night. 

I was lying in bed doing a cleansing meditation before falling asleep. 

I began to see a grayish static floating out of my body in all directions while my entire body took on a colorful static (all colors randomly moving like static through my body) and I saw this bright beautiful white/pale yellow light in the very back of mind behind my closed eyes, it was so bright that my actual eyes reacted and moved down away from the light, when my eyes moved a huge ring of rainbow light came shining toward me like it was physically coming at me. 

I composed myself and went back into my cleansing state and it happened again, this time I tried not to look away and the white light still threw a huge rainbow ring of light toward me. 

This was the most beautiful light I have seen in meditation, or in waking “reality”. 

What did I experience, what was this light?”