The idea it works is people send in their rejected toys that will become donors for damaged toys. Later on, senders receive a message notifying them how the donation supported and a picture of a toy fixed using parts from the donation.
The whole project is a good metaphor that gives a deeper perception of how organ donation works and the necessity of it. In Japan alone, around 14,000 people are on helping lists and only about 300 of them per year receive the organs they need.
You can also participate in the project, head over here for the details.