Creative Commons is a set of public copyright licenses that enable free distribution of an otherwise copyrighted work and allow copyright owners to specify what rights they are granting. Copyright owners can clearly designate the extent of reuse rights and users get certainty about what they are allowed to do.
Attribution. The most open of the CC licenses, CC BY requires only attribution of the copyright owner. Users can reuse, revise, remix, redistribute, and retain the content.
Others can remix, tweak, and build upon your work even for commercial purposes, as long as they credit you and license their new creations under the identical terms.
Allows for redistribution, commercial and non-commercial, as long as it is passed along unchanged and in whole, with credit to the copyright owner.
Allows for remixing, tweaking, and building upon copyrighted work non-commercially.
Allows remixing, tweaking, and building upon copyrighted work non-commercially, as long as the owner is credited and license new creations are licensed under the identical terms.
Allows downloading and sharing of the copyrighted work as long as owner is credited. Neither derivatives nor commercial use of the work is allowed.