There are six Creative Commons (CC) licenses. These CC licenses indicate the use parameters that have been granted by the content creator. The content creator still owns the copyright to that content, but through the selected CC license the creator is granting re-use of the content under the specified parameters. There is more on the history and uses of CC licenses on the Creative Commons Website.
Disclaimer: This information on Copyright, Fair Use and Creative Commons Licensing should be read for informational purposes only. This site nor any of its contents constitute legal advice.
It is possible as a content creator to relinquish your copyright claim on that creation. Creative Commons also has a Public Domain or CC0 license that marks a work as completely open; there are no restrictions and the creator does not have to be credited if you re-use this work.
Find out more at the Creative Commons Public Domian page.