Choosing the license for your published work allows you to decide how others may use it. When publishing your work with a traditional journal or publisher, you may sign an agreement where your work's copyright is transferred to the publisher, or you may advocate for retaining your rights as an author. According to the Copyright Alliance, "a copyright exclusive license is one in which ownership in one or more of the copyright owner’s rights is transferred by the copyright owner to a third party." In contrast, a non-exclusive license allows the copyright owner to retain the copyright and allow others certain licenses to the work as well.
See the Copyright Alliance's list of copyright exclusive rights to better understand the rights that licensing a work can give.
Using a Creative Commons license for your work allows you to specify how others can interact with your work.
Creative Commons licenses gives authors and creators control to choose which rights are important to them and which they do not wish to reserve; you can say "some rights reserved" instead of "all rights reserved" and give the public more permissions to your work than is typical under copyright.
From the same group of lawyers, professors, and advocates that brought us Creative Commons, the Science Commons gives scholars a variety of addenda to add to a publication agreement in order to help authors retain more of their rights.
