Creative Commons copyright licenses allow creators to retain their copyright while to granting specific permissions to others to share, use, and/or build upon their creative works. They are assigned by creators to their own work. Educators often use CC licenses so others can adapt/share/reuse learning materials.
To determine if Creative Commons licensing is right for you as a creator, or to understand how to interpret a Creative Commons deed for reusing works created by others, consult the following resources:
Public Domain materials are works that are free from intellectual property laws. There are no restrictions for individuals to use these works, nor are permissions necessary. Works within the Public Domain can never be owned by any individuals. There are different ways that works become part of the Public Domain. These include:
Expiration of copyright period (please see Cornell University's Copyright and Public Domain Guide)
Failure to comply with copyright formalities
Intentional dedication to Public Domain by the creator
Federal employees' works
"Common heritage of sources, or folk customs."
They belong to the public. However, citation is still required for remixing and reusing public domain works. Additionally, keep in mind that copyright laws and designations of the public domain vary by country.
Resources for Public Domain can be found in Additional Resources.
Creative Commons licensed works are free to use, but you must follow the terms of reuse. Check the text of the full deeds (links below) to understand the scope and/or restrictions of the licenses:
Summary: Allows others to remix and build upon your work, even for commercial purposes, as long as there is proper attribution and the new work is issued under the same licensing terms. This license is often compared to “copyleft” free and open source software licenses.
Summary: Allows redistribution of works for both commercial and non-commercial purposes, as long as it is passed along unchanged, in whole, and with proper attribution.
Summary: Allows others to remix and build upon your work non-commercially. Although the new works also must acknowledge the creator and carry a non-commercial license, the new or derivative works created do not have to carry the same terms.
Summary: Allows others to remix and build upon your work non-commercially, as long as proper attribution is followed and new works are licensed under the same terms.
Summary: Allows others only to download your work and share it for non-commercial purposes as long as the work remains in its original format. This is the most restrictive of the licenses.
Summary: Allows creators to waive most copyrights to their original works, allowing others to reuse, share, and remix freely with proper citation. This is the least restrictive of the licenses.