Surfacing is adding a material to the surface of a board.  This is like a veneer or laminate.

 

You must create the surface material in the surface database.  You can determine the color of the material to be applied.  The advantages of using surface material are that the board is the desired color or texture, the surface material is added to the parts list [with the cost included], and the surface material is passed to the optimizer to provide the most efficient layout pattern.