Copyright and other laws throughout the world automatically extend copyright protection to works of authorship and databases, whether the author or creator wants those rights or not. CC0 gives those who want to give those rights a way to do so, to the fullest extent allowed by law. Once the creator or subsequent owner of a work applies CC0 to a work, the work is no longer his or hers in any meaningful sense under copyright law. Anyone can then use the work in any way and for any purpose, including commercial purposes, subject to other laws and the rights others may have in the work or how the work is used. Think of CC0 as the "no rights reserved" option.