While both light and sound travel as waves, the speed of light is much, much faster. Light is composed of electromagnetic waves which travel independent of a medium. That is to say, light can travel in a vacuum, such as outer space.
Electromagnetic waves travel very fast.
However, when light passes through transparent materials, it slows down a bit. This is because electromagnetic waves interact with the subatomic components of matter. In water, for example, light slows down to around 0.75c, or 225,000,000 meters per second. Sound is created by small changes in pressure near the surface of a vibrating object. These changes are propagated through a material medium, such as air, like the ripples formed when one tosses a stone into a pool of water.