Copyright is a form of protection, provided by law, which protects the original works of authors and creators. It protects expressive content and grants rights to authors for the protection of their work.
The owner of copyright has the exclusive right to:
License others to engage in the same acts under specific terms and conditions
A copyright owner's rights are extensive but not absolute--they can be 'unbundled' and transferred to someone else (such as when an author signs over distribution rights to a publisher). There are also limits on the duration of rights and some limited exceptions under the law, including fair use and classroom instruction.
Creative Commons is a nonprofit organization that provides licenses and tools for users to grant copyright permissions for creative and academic works. An author can use a Creative Commons (CC) license when they want to give others the right to share, use, or build upon a work they have created.
With a CC license, the author retains copyright but the license allows others to copy and distribute their work provided they give credit — and only use the work according to the conditions specified in the license.
The video below (created by Creative Commons and available via a CC BY-SA license) briefly explains.
Below you will find information on the different CC licenses available.