Rapid Manufacturing is just taking Rapid Prototyping one step further.  Most parts made by Rapid Prototyping are only used in the design or testing phase.  Rapid Manufacturing means making finished parts that become the final product.  This is not however, mass production and therefore the numbers usually only range from a single piece, to a few dozen, to a few hundred items.  Rapid Manufacturing is often called on-demand manufacturing.  Rapid manufacturing is a relatively new development.  This is mainly due to the advance in materials.  In past year the parts made by Rapid Prototyping would not have been durable enough for use as the finished part.  However, with newer materials like ABS plastic the parts are fully functional and are not limited to form and fit testing.  The materials used in Rapid Prototyping and manufacturing are only getting better, allowing more finished parts to be created with Rapid Manufacturing.  Just like Rapid Prototyping, Rapid Manufacturing uses .STL files to transfer data.  The advantages of Rapid Manufacturing include: the elimination of tooling and tooling costs, higher production speed and low production cost overhead.