No matter how complex your product or story, you can always convey it using the technique described below. Start with a description of the main characters. Explain the big picture with a trailer image. Then pick a scenario that conveys the main value the product brings to the table and use that scenario to explain the main value your product provides to users. Once you identify these things and validate this hypothesis with your users and customers, the rest becomes easy.
Let us say you are building a product called Doctor's Place. It is a collaboration tool that helps patients and doctors keep in touch with each other. How do you go about visualizing what the tool might do.
The main scenario that conveys the essence of your product.
Presenting your story
Chances are you will end up presenting your story in different kinds of sessions. Some may be an hour long. Some may be just ten minutes. If you have less than ten minutes, just show the trailer and convey the hypothesis. If you have about 45 minutes, then go into the scenario and explain the main concepts.