Creative Commons
A Creative Commons designation indicates the work is still protected under copyright but can be used as long as the required conditions of the creative commons license are enforced.
For example, this designation indicates the user can freely use the work as long it is properly cited (ex. BY Jane Doe) and the new user licenses any new creation under the same Creative Commons license.
Other categories of CC licenses can stipulate additional requirements such as reproduction can be for non-commercial use only, or that no derivative work or alteration to the original work is allowed.
To learn more about both sharing and using follow this link to the Creative Commons.