A sample model of an application without functionality
is know as prototype.
       As soon as the company receive the requirements
from the client,project manager review the requirements
and he prepare a sample application based on the 
requirements,based on the sample applications developer
design the application.

Prototype is nothingbut mockup of the application after 
getting requirements from the client pm makes sample 
application it will be having all the functionalities but 
they will not work.It looks like a  application but not at 
all application

Its a dummy model........containing same features of 
original one...

              whenever customer or client is new to the IT 
industry,by that time v r going to use prototype model

Developing a structure which is not completly implemented is
called prototype
It works well for smaller applications

if any thing wrong in my answer plzz mail me correct answer
sridharraghava@gmail.com