I would explain to an employer that a script or storyboard is a written plan for what will be said, how the project will flow, and what will be on the screen as the video moves along. Both help everyone working on it picture the finished product before we spend time creating it.
A script and storyboard can function like plans for building a house. We use it as the plan so everyone understands what we are working toward and how all the pieces fit together. The team can review the message, suggest changes and make sure its exactly what they want before putting the time in of making it and changing it later.
