Creative commons (or CC) is a type of license that eschews some conventional protections of copyright, but may retain others. The license is defined by the creator at the time of publication. As the CC website puts it - they 'let you change your license from all rights reserved, to some rights reserved.' (creativecommons.org).
Check out some of the licenses below to get an idea of the different types of licenses available.
When combining or 'remixing' two items that have creative commons licenses, consult this chart to make sure the different licenses are compatable.