Creative Commons (CC) licenses are public licenses. You can use them to indicate what other people are allowed to do with your work. Each work is automatically protected by copyright, which means that others will need to ask permission from you as the copyright owner.
CC licenses let you easily change your copyright terms from the default of “all rights reserved” to “some rights reserved.” They are legal tools to give permission in advance to share and use your work – on conditions of your choice.
There are six different Creative Commons licenses: CC BY, CC BY-SA, CC BY-NC, CC BY-ND, CC BY-NC-SA, CC BY-NC-ND. The letter pairs indicate conditions for use.
CC BY is the most open license. It allows the user to redistribute, to create derivatives, such as a translation, and even use the publication for commercial activities, provided that appropriate credit is given to the author (BY) and that the user indicates whether the publication has been changed.
CC BY-SA is also an open license. The letters SA (share alike) indicate that the adjusted work should be shared under the same reuse rights, so with the same CC license.
NC (non-commercial use) and ND (no derivative works) are conditions that make the CC licenses more restrictive and thus less open.
The figure below shows a good overview of what each license permits you to do.
Creative Commons licenses by Foter (CC-BY SA)
In Open Access Publishing and in Open Educational Resources CC licenses are commonly used.
For more information, visit the website Creative Commons, About the licenses.