Creative Commons provides a range of licenses, each of which grants different rights to use the materials licensed under them. All of these licenses offer more permissions than “all rights reserved.”
To help show more clearly what the different CC licenses let people do, CC marks the most permissive of its licenses as “Approved for Free Cultural Works.” When you apply these licenses to material you create, it meets the Freedom Defined definition of a “Free Cultural Work" (Freedom Defined is an open organization of free culture advocates and researchers; the definition was developed by its community as a parallel to efforts such as the Free Software Definition, to have a standard for defining Free Culture). Using that definition, material licensed under CC BY or BY-SA is a free cultural work (so is anything in the worldwide public domain marked with CC0 or the Public Domain Mark). CC’s other licenses– BY-NC, BY-ND, BY-NC-SA, and BY-NC-ND–only allow more limited uses, and material under these licenses is not considered a free cultural work.
The following graphics appear in CC's license chooser to distinguish these two categories of licenses:
This graphic means that a license is “approved for free cultural works” under this definition. (These licenses are sometimes referred to as “free licenses.”)
This graphic means that a license is not approved for free cultural works.
Free cultural works are the ones that can be most readily used, shared, and remixed by others, and go furthest toward creating a commons of freely reusable materials (Source).
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