Copyright is a set of laws that protect "original works of ownership" for literary, dramatic, musical, artistic and other intellectual works. The law protects both published and unpublished works. However, it does not protect ideas. Rather, it protects the expression of ideas.
Copyright applies at the point of creation and registration is not needed for copyright protection to apply.
Copyright law give the creator the exclusive right to do the following with their work:
Individuals who violate these creators' rights can be held liable for copyright infringement. To avoid infringement of protected works, individuals wanting to use a specific protected work can seek permission from the creator (which may require paying royalty fees) or use an amount that meets the fair use criteria outlined in the law.
Source: United States Copyright Office. Copyright Basics (Circular no. 1). https://www.copyright.gov/circs/circ01.pdf