Light is an electromagnetic wave. What that means is that it is an oscillating electric and magnetic field. An electric field, is what causes the attraction between a positive and a negative charge. A magnetic field cause the attraction between the North and South poles of a magnet. In light, the strength of these fields changes with time and place. How fast this wave changes with time and place determines what color the light is.
I can't tell you why light travels so fast. I can tell you one interesting thing though. Albert Einstein showed that light is the fundemental speed limit in the universe. Nothing with mass can move as fast as light.
