Light!What is light?

Light is the form of electromagnetic radiation which enables us to see by bouncing back or reflection of the light,it can also travel in vacuum .For example: Rays of sunlight has to pass through the vacuum to reach the surface of earth .Light is mainly produced by heat but we cannot say that it is only produced by heat because many substance like: fireflies do gives out their own light but didn’t use heat to produce light .Where there is no light its the place where dark matter exist .