Creative Commons licences (CC)¶
Creative Commons is a complement to copyright that addresses authors wishing to :
Share and facilitate the use of their creation by others
Allow free reproduction and distribution (under certain conditions)
Grant more rights to users by supplementing the default copyright
Develop a work and enrich the common heritage (common property or Commons)
Save transaction costs
The 4 options that make up the 6 licenses :

CC licenses are non-revocable: an author can decide at any time to distribute his works under other conditions, or even to stop distributing them under CC but the effect of the CC license cannot be withdrawn on copies of works that circulate or will have already been distributed, including in adaptations or collections that include the work.
If there are several authors, consider getting the agreement of your co-authors.