Owners hold specific rights but not all rights.
The law grants to owners a set of specified rights: reproduction of works; distribution of copies; making of derivative works; and the public performance and display of works. Some artworks have "moral rights" regarding the name of the artist on the work, or preventing destruction of some works. Owners may also have rights to prevent anyone from circumventing technological protection systems that control access to the works.
Author is the copyright owner.
As a general rule, the initial owner of the copyright is the person who does the creative work. If you wrote the book or took the photograph, you are the copyright owner.
Employer may be the copyright owner.
If you created the work as an employee, acting within the scope of your employment, the work may be a "work made for hire." In that event, the copyright owner is the employer. If you are an employee, and your job is to create software code, the copyright probably belongs to your employer.
Copyrights can be transferred.
The law may make you or your employer the copyright owner, but the law also allows the owner to transfer the copyright. With a written and signed instrument, your employer can give you the copyright. In the academic setting, we are frequently asked to transfer copyrights in our books and articles to publishers. The ability to transfer or retain our copyrights is an opportunity to be good stewards of our intellectual works.
Copyright owners may allow public uses.
A copyright owner may grant rights to the public to use a protected work. That grant could be a simple statement on the work explaining the allowed uses, or it may be a selection of a Creative Commons license. Similarly, the movement to make works "open access" or "open source" is a choice by the owner of rights to make works available to the public.
Used under a Creative Commons BY license from the Copyright Advisory Office of Columbia University, Kenneth D. Crews, director.