A storyboard (in HCI) is a comic-strip-like set of drawings about what your interface does and how it is used to accomplish tasks in a real usage scenario.
A good storyboard should clearly demonstrate who the user is, the usage situation, and the user's motivations for using the interface.
It should show what the user can accomplish with your interface, but it needn't (and often shouldn't) show a specific user interface design.
- People involved?
- Task being accomplished?
- What steps are involved?
- What leads someone to use the app?
- What task is being illustrated?
- What's the motivation for the user?
- What's the end result?
- What need are you "satisfying"?