Commercial (Paid) Books:
Your book is private and only accessible by you.
You have exclusive copyright and are free to use the book however you wish.
You can sell, distribute, or modify it without any restrictions.
Free Books:
The book will be published on the Youbooks website.
It will be available for anyone to download.
You cannot publish or commercially exploit free books.
Attempting to publish a free book may result in banning of your publishing account.