By BLUE FOX Creation
Diffuse map : The most frequently used texture mapping method. It wraps the bitmap image onto the 3D geometry surface while displaying its original pixel color. It's a standard photo that you'd get if you stood in front of the material and photographed it.
Albedo : An albedo texture is very similar to a diffuse map, but with one extra benefit: all the shadows and highlights have been removed.
Bump map : Bump mapping uses the grayscale values of an image map to create variations in the shading of the surface to which the map is applied. It adds details to 3D models without increasing the number of polygons.
Normal map : A Normal map is usually made from a high polygon model. Its color representation will affect surfaces like a regular bump map while providing higher degrees of detail.
Specular/reflection map : control how reflective the surface is, and can adjust the shape of the reflection. Specular usually simulates only the reflections of the brightest light sources in a scene.
Gloss/Roughness map : Roughness maps are Gloss maps in a PBR system, representing how smooth or rough a surface is. Also called Microsurface.
Displacement maps : Displacement maps are similar to bump but store height information and modify geometry when rendered, modifying both appearance of shading and silhouette.
Emission map : Emissive map (aka Glow or Self-illumination) mimic surfaces that emit light, like a computer monitor, a vehicle dashboard at night, or magical effects.
Ambient occlusion maps (AO) : Ambient occlusion maps are pre-computed calculations of ambient light bounce on a surface.
Cavity maps : Cavity maps are narrower version of ambient occlusion, keeping dark shadows to crevices and sharp corners only(usually used in metalness workflow).
Opacity/Alpha maps : Opacity maps, also known as Transparency map, are used to cut out parts of a surface, usually for alpha blending. For example: fire, grass, hair, smoke, water, windows, etc.
(Reference : polligon,polycount-wiki,iclone...)