Creative Commons defines the spectrum of possibilities between full copyright — all rights reserved — and the public domain — no rights reserved. The licenses help to the author to keep its copyright while inviting certain uses of its work — a “some rights reserved” copyright.
Many of the licenses, notably all the original licenses, grant certain "baseline rights", such as the right to distribute the copyrighted work without changes, at no charge. Some of the newer licences do not grant these rights. Creative Commons licenses are currently available in 34 different jurisdictions worldwide, with nine others under development.
The original set of licences all grant the "baseline rights". The details of each of these licences depend on the version, and comprises a selection of four conditions:
Mixing and matching these conditions produces sixteen possible combinations, of which eleven are valid CreativeCommons licenses.
Contributors to the eMapps.com learning object repository can choose either to make their objects publicly available without any licence restrictions or to apply a CreativeCommons Licence. In the latter case, the user is prompted to select to allow or disallow commercial use and to allow or disallow modification of the object, or to allow modification only if further use is shared. The appropriate CreativeCommons licence is then automatically applied, including the requirement for attribution. Project participants have been encouraged to be as open as possible in granting permission for re-use."
More information on the CC approach: http://creativecommons.org/