Mapping coordinates are the parameters that are used to tell a renderer where a bitmap should appear on the geometry. Mapping coordinates specify the placement, orientation, and scale of a texture map (for example a bitmap or a procedural map) on the geometry.
If a mapped material is applied to an object that has no mapping coordinates, the renderer assigns default mapping coordinates. The built-in mapping coordinates are designed for each object type.
Maps have a spatial orientation. When you apply a material with maps in it to an object, the object must have mapping coordinates. These are specified in terms of UVW axes local to the object.
Some objects, such as editable meshes, don't have automatic mapping coordinates. For these types of objects, coordinates are assigned by applying a UVW Map modifier. A UVW Map is also used to change an object's default mapping.