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Light is a form of energy and travels as a wave in straight lines. We see things when light hits them and bounces off and enters our eyes. Objects that create light are sources of light and we call them luminous objects, for example, the Sun. We see them because light from them enters our eyes. Light bounces off non-luminous objects (for example, the moon) and we see them because that light enters our eyes once it has bounced off the object.
Light travels faster than sound. We know this because of examples such as thunder and lightning - we see the lightning first and then hear the thunder, but they actually occur at the same time. Another example is dropping an object such as a book - we will see the book hit the floor before we hear the thud. The speed of light is 300,000 km/s (kilometres per second). It takes 8 and a half minutes for light from the Sun to reach the Earth.
When we shine a laser ray (a very narrow beam of light) we can see that light travels in a straight line. Shadows are made because light does not travel through some objects, and so a shadow appears behind these objects (on the opposite side to the light source).
