Having a strong storyboard is the easiest and most efficient way to ensure that your clients get the best presentation of the final product.
It is true that a picture tells a thousand words, so no matter how well you try to explain your idea of the advert it is very difficult for your client to imagine the final idea. It is much easier and more reliable to show it step by step in frames; the same environments, characters, clothing, style, general lighting...

Activia Stardust

Gas Natural 300

Sanex Petrocolor