The 3D design can be printed using a 3D printer on a small or larger scale as a mock of the real object. However, the materials in the printed object are mostly not the same as in the real world hence in some cases even the functionality would be the same. The most purpose of this is to get a sample as close as the real world.
Printing your 3D design is a good way to feel what your product actually is:
Our specialty 3D printers can do a loooooooooong unlimited print!
Other specialty 3D printer that does CNC and laser too!