Retro-reflectivity is the correct term given to something that has the ability to return light back to it's source. Many items are reflective, white paper, metal foil, a mirror.  All of these are reflective but the light reflecting off them is scattered in many directions. None have the ability to return a large proportion of the light back into the direction from where it came.

Where will I have seen it?

When you've seen the Emergency Services on TV at an incident at night and the marking and the tape on their clothing shines bright light. This is because there is a source of light on or next to the video camera, this light is hitting thee retro-reflective material and is being reflected directly back to where it came from, (into the camera) There wearing becomes therefore far more visible in dark or low light conditions. If you are a driver you will be aware that the road signs are also made of retro-reflective material.

Aging of the Eyes

After the age of 20, a person's illumination needs double after 13 years.

1989 ITE Compendium of Technical Papers