A concept is a clearly articulated idea. Often this idea combines functionality and benefits of a service.
To create a concept, it’s best to look back at the ideas created in your design workshops. Group them into themes and summarise a product or service that addresses them in a sentence or two.
Relate each concept back to the proposal. Define who the primary end user is for each concept and describe the benefits they will experience from using your concept.
You may end up with a few concepts as a result of this activity. Start to validate each one by thinking about how realistic it is, how useful it is likely to be, and how original it feels (see validate a concept).
Refine your concepts further by combining those that address similar needs for similar users, then select a shortlist of concepts that show the most promise. Define the user experience for each of them, all the while thinking about how a user would interact with that concept to help tell the story.