What
Storyboarding is a narrative technique or arranging a series of illustrations in sequence in order to pre-visualize a motion graphic or human product interaction.

They are normally presented as a series of frames, which show an event like a user journey or interaction. The form varies from the very sketchy to very detailed depending on whether they are used to report on existing situations, present new ideas or design concepts for discussion.

Why
Storyboards help to visualize context and time. They are increasingly being used in interaction and service design to communicate a users actions as well as the context – place, situation, social setting in which a product or service is used.

Storyboards are often used with other design tools such as role-playing, quick and dirty modelling sketching, and use-scenarios.

When 
Soryboarding can be used at various points in the design cycle. To help shape early ideas, to explore implications of a design decision, to illustrate the context of a proposed solution.

Photo Storyboarding is a quick and collaborative technique for building storyboards in which teams act out a narrative using simple props. The props may be white card cut outs to represent a product. Digital photos of the action are quickly printed and used to form the storyboard. These images can be sketched over, cropped and props annotated.

Getting service users or clients to join in acting out the story will bring new insight and understanding.

In physically making a storyboard teams are confronted with a diverse range of questions and design implications, which may otherwise be post-poned with more abstract considerations.