Rapid technology prototyping, alternately referred to as 
rapid prototyping (RP), is currently the most advanced method for 
quickly creating a prototype.
This
 technology is accomplished by using a rapid prototyping machine. Rapid 
prototype machines can produce prototypes in mere hours.  Depending on 
the complexity of the prototype, it may take anywhere from just a few 
hours to a few days for its completion.
Rapid technology 
prototyping is also commonly called solid free-form fabrication, layered
 manufacturing, or computer automated manufacturing.
The benefits of using rapid technology prototyping are...
»Any object of any complexity can be formed fairly easily and quickly without the need for machine setup or assembly.»Objects are made from multiple materials or as composites.
»Since usually only a single unit is produced, the costs can be kept down to a bare minimum.
Here's a brief explanation of how it works...
Basically,
 rapid technology prototyping takes traditional 2 dimensional printing 
and adds a third dimension to it.  Therefore, rapid prototyping machines
 are fondly called 3 dimensional printers.   Rapid technology 
prototyping takes a Computer-Aided Design (CAD) model and using a laser,
 creates a physical model out of a variety of media.  The media types 
include paper, ceramic material, wax, or even plastic.
In contrast
 with most machining processes, rapid technology prototyping is an 
"additive" technique.  This means layers of media (whether paper, 
ceramic, wax or plastic) are combined to create a 3-D solid object.  
Most machining processes, such as drilling and grinding, are 
"subtractive" techniques, where material is removed from a solid block.
The process of rapid technology prototyping is listed out below ...
»First, you need a CAD model of your invention.»Next, the CAD model must be converted to STL (stereolithography) format. This file represents your invention as a series of triangles like that of a cut diamond. STL does not represent curved surfaces, only cut surfaces. However, you can create what appear to be curved surfaces by increasing the number of triangles.
»The STL file will need to be sliced into layers from 0.01 mm to 0.07 mm thick, depending on the build technique you choose.
»Construction of the object takes place layer by layer. The rapid technology prototyping machine builds the layers from the selected media.
»The final step is to clean and finish the prototype. In many instances, it will be sanded, polished or painted.
What is it used for?
Rapid technology 
prototyping is commonly used by inventors to help communicate their 
invention to a patent attorney or a trade representative.  It may also 
be used for gaining manufacturing quotes, trying to sway investors and 
in marketing focus groups.  As you can imagine, it is much easier to 
communicate an invention using a 3-D prototype than with a 2-D drawing 
or blueprint.
What does it cost?
Of course,
 costs range due to the complexity and size of your invention.  They can
 also increase if you need additional design work such as painting done.
  Smaller prototypes can be made using rapid technology prototyping for 
about $250.  You can gain an estimate by calling several companies.
There
 are limitations to rapid technology prototyping, but it truly is 
revolutionary.  In the past, inventors had to wait weeks, sometimes up 
to months and pay much higher fees to have a single prototype made.
It
 is also possible to use rapid technology prototyping for making tools. 
 This technique is known as rapid tooling.  In addition, it can even be 
used for the production of parts and manufactures, known as rapid 
manufacturing.
