Creative Commons makes use of four different license

conditions—attribution, share-alike, noncommercial, and no derivative

works—in varying combinations to create six distinct, and free, usage

licenses. Several million pages of web content are currently governed

by Creative Commons licenses.

The attribution tag permits others to copy, distribute, display, and

perform your copyrighted work — and the derivative works based upon it

— but only if they provide you with the credit you request.

"Share-alike" permits others to distribute derivative works but only

under a license identical to the license that governs your work. The

non-commercial tag lets others copy, distribute, display, and perform

your work — and derivative works based upon it — but for noncommercial

purposes only. And "no derivitive works" lets others copy, distribute,

display, and perform only verbatim copies of your work, not derivative

works based upon it.