Follow m on this, it may take a bit to explain properly.
Creative Commons License.
It's a copyright license that allows works to be shared, used and reworked, depending on the license, without having to gain permission from the original creator. Most of these licenses allow use of the content in some form as long as the original creator is credited.
Why would you ever want to release your work under a CC license? Why wouldn't you just want to stick with a basic copyright and keep complete control over it?
Seems crazy, but here is the thought process:
A lot of people will love a series and its characters, creating libraries of their own fiction, designing wardrobes full of t-shirts and accessories and redrawing the characters into every scene imaginable. All of this done with them only loving the series from the outside, having no real owner ship of the work. The greatest thing that can happen to a series is for it to develop a devoted fan base, one that grows, gets excited and shares what they love with others.
Now here's the thing. How much more would the people in the fan base love something, how much more time would they give to their projects based around it, if they could call it their own too? If they could create and sell their own works based off the original series, with the blessings and support of the original creator?
Take a series, create characters and supporting cast, imagine up a whole world of stories, and then turn it over for any and everyone to join in and create content for. Using a Creative Commons license like Attribution and Attribution-ShareAlike, you can create work and allow it to be shared, tweaked, remixed, and built upon commercially. All works that use your work though must give credit as well as keep their material under the same Creative Commons Licenses so others can use it too.
Imagine a community creating and building upon itself. The original creator sets up a world and characters people like. One of the fans likes a certain character more and makes their own webcomic about that character. Someone else likes the costume design the fan added and makes a real version to sell on their site. The original creator sees the clothes, loves them and turns around and incorporates them into another story with that character, but now with the fan made content.
Even if someone used the characters and had a lot of commercial success with it, the original creator would still benefit from it. So someone makes another video based off the original work, and it get millions of views. People who like the new video will also come across the original work, expanding the fanbase further than the original content could on its own.
Also since the original CC license states that all work using that content must also be released under the same CC license, everyone would share in its success and could build off it again. Someone could take the idea and run with it, making bigger and better things based off of the original, but they would all be tied together and no one could cut others off from taking that work and making something based off that.
To learn more about Creative Commons Licenses, hit the link