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. Creative Commons licenses could be applied to all work falling under copyright, including: books, plays, movies, music, articles, photographs, blogs, and websites.
There are several types of Creative Commons licenses. The licenses differ by several combinations that condition the terms of distribution. They were initially released on December 16, 2002 by Creative Commons, a U.S. non-profit corporation founded in 2001. Released in December 2018, the 4.0 license suite is the most current.
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.
For more information check the following page.