* Stars are giant balls of hot gas undergoing nuclear fusion. This process releases tremendous energy in the form of light and heat.
* Planets are much smaller and cooler. They don't have the mass or internal processes to create their own light.
* Planets shine because they reflect sunlight. The sunlight that hits a planet gets scattered in all directions, making the planet visible to us.
Think of it like this: a mirror doesn't produce light, it simply reflects the light that shines on it. Planets are like giant, slightly less reflective mirrors, reflecting the light from our sun.
