Bump Maps These are based on greyscale images. The bump shader recognises the shades of black & white and, using white for up and black for down, gives the material the illusion of height & depth. These are calculated at the point of render.
Normal Maps These are similar to Bump maps but are based on RGB (for RGB read XYZ) Unlike bump maps, these are pre-calculated and therefore speed up render times. They nearly always appear turquoise in colour as the Z value is the blue channel Easy to create in UVW Unwrap editor, Render to texture , Photoshop, CrazyBump etc.
Displacement Maps These are based on greyscale maps where white is up & black is down. They differ from Bump & Normals in that they actually do change the geometry of a model. If used in a displacement channel of a material, the effect will be calculated at the point of render and will NOT be seen in the viewport. If it is used as a displacement modifier,the effects will be seen in the viewport and there is much better control over it.
Opacity Maps These are black & white masks of the diffuse map that when applied to the opacity channel in a material, only the image required will be seen. Black areas become transparent whereas the white is visible.
Camera Mapping This allows the user to map a digital image onto a primitive model. It gives approximately 6 – 8 degrees of movement until stretching occurs in the image. Great for creating a photorealistic environment where camera movements are limited.
Remember... if the world didn't suck... we'd all fall off!