A copyright owner gets to do, or authorize others to do, the following things: U.S. Copyright Code, 17 U.S.C. § 106
A copyright owner can dole out some or all of those rights to other people or entities, by transferring ownership or granting licenses. Ownership or license rights can be shared by any number of people or entities.
By default, publishing contracts often transfer all of these rights from the author to the publisher. In cases where this has been done, an author may be forced to request permission to exercise the rights he or she no longer has. Before signing contracts, be sure you understand which rights you can retain in your own work.