Elements

Creative Commons licenses are composed of its logo plus at least one of four elements:

By (attribution), NC (noncommercial), SA (share alike), and ND (no derivatives).

Types of licenses

These four elements combine to build the six different types of Creative Commons licenses below.

Attribution (CC BY)
The basis of the other five CC licenses, CC BY is the most accommodating of licenses offered. This license lets others distribute, remix, tweak, and build upon your work, even commercially, as long as they credit you for the original creation. Recommended for maximum dissemination and use of licensed materials.

Attribution ShareAlike (CC BY-SA)
This license lets others remix, tweak, and build upon your work even for commercial purposes, as long as they credit you and license their new creations under identical terms. This license is often compared to “copyleft” free and open source software licenses. All new works based on yours will carry the same license, so any derivatives will also allow commercial use. This is the license used by Wikipedia, and is recommended for materials that would benefit from incorporating content from Wikipedia and similarly licensed projects.

Attribution-NonCommercial (CC BY-NC)
This license lets others remix, tweak, and build upon your work non-commercially, and although their new works must also acknowledge you and be non-commercial, they don’t have to license their derivative works on the same terms.

Attribution-NonCommercial-ShareAlike (CC BY-NC-SA)
This license lets others remix, tweak, and build upon your work non-commercially, as long as they credit you and license their new creations under identical terms.

Attribution-NoDerivatives (CC BY-ND)
This license allows for redistribution, commercial and non-commercial, as long as it is passed along unchanged and in whole, with credit to you. Please note that you can revise the work for your own use. You just can’t distribute it in the adapted form.

Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND)
This license is the most restrictive of the six licenses, only allowing others to download your works and share them with others as long as they credit you, but they can’t change them in any way or use them commercially.

In addition to the six licenses, two public domain tools apply to OER:

Public Domain Dedication (CC0): CC0 enables scientists, educators, artists and other creators and owners of copyright-protected content to waive those interests in their works and thereby place them as completely as possible in the public domain.

Public Domain Mark (PDM): The Public Domain Mark enables works that are no longer restricted by copyright to be marked as such.

The chart below lists the licenses from the most open to the most restrictive.