Auto Reflection makes materials with words like metal or plastic in them reflective based on the words in the material name - without having to set material properties for each material individually.
This can make it easier to get photo realistic results from models - especially models with components in them which use materials which you did not create or define - without having to spend time to set basic reflection, or other material properties on each the materials.
For example, you can specify that all materials with the word "steel" in them should be 90% reflective and metallic.
Any materials with the matching words in them, and for which you have not already set specific material properties, will get the properties from the Auto Reflection Wizard.
(If you do set material properties your self for a material, those settings will override the Auto Material settings.)