Creative Commons licenses combine terms to form a single license, for example "BY-NC-SA" and "BY-NC-ND". "BY" is a part of every license. For detailed definitions, consult the Creative Commons website. Below is a brief summary:
Attribution (BY): You let others copy, distribute, and display your copyrighted work - but only if they give you appropriate credit. All Creative Commons licenses have this requirement.
Noncommercial (NC): You let others copy, distribute, and display (and possibly adapt) your work - but for noncommercial purposes only.
No Derivative Works (ND): You let others copy, distribute, and display only identical copies of your work - but not translations or other derivative works based upon your work.
Share Alike (SA): You let others distribute adaptations, translations, or other derivative works - but only under a license identical to the license that you chose for your work.