GreyScale = form Black to White, most times Black is none, white is full effect.
Color+AlphaMap, Colorinformation in RGB and a Alpha Channel for Transparency.
Games use the Alpha to cut “holes” in an Object.
In a render it just reveals the surface below it. You can put multiple ColorMaps over each other, a bit like Layers in PhotoShop.
DiffuseMap, GreyScale, Lightabsorbation of a Surface (dont know how this is called in MAX)
BumpMap, Greyscale, Heightinfo for Lights
NormalMap, Vectorinfo for Lights in RGB, AlphaChannel used for Parallax Effect(GreyScale)
Tangent (blueish map, can deform and rotate)
ObjectSpace (RainbowColors, can rotate, not good for deforming)
WorldSpace (RainbowColors, dont touch )
I prefer Tangent because i dont have to think about future use of the object…
DisplacementMap, GreyScale (ZBrush uses 16-bit Tiff), a bit like BumpMaps but they actually deform the (Highres-)Mesh
SpecMap, Greyscale, Info for Specularity
Glossmap, Greyscale, Info for “Sharpness” for Specularity
ClipMap, B+W, used to cut “holes” into the Object.
LuminosityMap, Greyscale, used for Selfillumination (glowing Buttons, Displays etc.)
ReflectionMap, Greyscale, used to say where and how much reflection should be visible.
DetailMap, Greyscale, tileable, used to add “grain” to the texture, if you get close to an object it fades in and makes a “blurry” Texture a bit more intressting. I think in Serious Sam its just everywhere.
I never heard of DirtMaps. Whats that?
Sometimes you also have to create diffent maps not discribed here but are important for the Game.
I used a rainbowcolor map for terrain generation. Was ugly to look at but all the needed details where in there and had i higher Resolution that a simple 8-bit GreyscaleMap.
Tileable maps are used in LevelEditors like Unreal. You make a texture that repeats seamless on X… maybe also on Y.
The hard Way would be if the Map also could be rotated in 90° Steps. We used that in a game for the PS1 for a more “random” look. Also these Tiles had sizes like 25x7 Pixels because they where arranged on a TexturePage (1024x1024 if i remember correctly)
These are the things i have seen or used so far… hope it gives you a little overview.