Creative Commons provides a set of basic licenses that dictate how others can and cannot use your work. Specifically, the licenses indicate whether your work can be used by others for commercial purposes, whether others can create derivatives of your work, and whether others must use the same CC license after adapting your work.
The most liberal of these licenses (CC-BY) tells others that they can use your work however they like as long as they give you credit. In contrast, the most conservative license (CC-BY-NC-ND) indicates that your work cannot be adapted and cannot be used for commercial purposes. Don't forget also that if you want to dedicate your work to the public domain, you can use a CC0 license. This, of course, is your most liberal option for sharing work.