Here's a breakdown:

* Reflection: The bouncing back of light when it strikes a surface.

* Reflectivity: The measure of how much light is reflected from a surface. It's often expressed as a percentage.

For example:

* A mirror has very high reflectivity, reflecting almost all the light that hits it.

* A black surface has very low reflectivity, absorbing most of the light that hits it.

Let me know if you'd like to know more about reflection or reflectivity!