Material properties define the 'glossyness' of a material, and the colour it shows in this glossyness. By glossyness I mean like the 'hotspot' on a snooker ball under a bright lamp.

The reflectivity is set by the alpha channel in the texture you apply to that material. Try making a flat plate and applying a fully reflective texture to it, you'll see that it reflect the sky and ground around it.

For an explanation, go to http://www.simcraft.nl/tutor_list.html and look at 'General topics' 1 through 4. This explains the priciple of material and textures, and how they interact.

Hope that helps,

Ric B.