As the project organizer, you can choose whether or not the members of your project can create chapters. Some project organizers may want to setup the chapters in their project themselves and may not want other members creating their own chapters. Others may want to give their contributors creative liberty to create fun and unique chapter titles for the final book. Here's what the two options for Chapter Creation Settings mean:
Normal
In Normal mode, all project members can create chapters for their stories and pictures. This lets an order and structure for your book develop organically as people participate.
Restricted
In Restricted mode, only you can create chapters and members of your project have to add their stories and pictures to the chapters.
Other Chapter Options
You can also create chapters ahead of time and assign them normal, restricted, and hidden values. That means that you can chose to set individual chapters to the following:
Normal: Everyone can participate.
Restricted: Everyone can see it but only you can add to this chapter.
Hidden: No one but you can see and add to this chapter.