A copyright gives you the exclusive right to reproduce or copy the work or change its form, like creating a sequel and revising or updating the work.
Only you can perform the work or display it in public; everyone else has to ask you first.
You're the only person who can distribute the work for commercial purposes.
You can sell your right to control over the copyrighted work, so when you write your next big thriller you can sell the movie rights and keep the right to create a sequel.
Registration informs the world that you own the work and all the rights of ownership.
Registration protects your rights in the twenty foreign countries that still condition legal protection on public notice that the rights have been claimed.
Your work will be in the Library of Congress!
You can't sue for copyright infringement or get an order from a judge to make somebody stop using your work unless your work is registered either within the three months after your work is first published, or before the infringement first occurs.
If you succeed in an infringement suit, you are entitled to money damages even if you can't prove how much money you actually lost because of the infringement.
If you succeed, the infringer will have to pay your lawyer.
Contact a qualified business attorney to help you identify how to best protect your business' intellectual property.