Hello everybody could someone please explain me how to make specular maps or is there any tutorial which would help me???

Brighter = more specular, darker = less specular. Some games allow for colored specmaps where the color of the map is the color of the specularity. If you mean implementing them, well, that depends on your engine or graphics API.

KDR- which games?

AFAIK Doom 3 does. I don't know of others though I'd guess HL2 would do that, too.