To download and share digital content legally and let people know that you want them to reuse your own work, creative commons licenses can help you do both when something like a photograph or a sound track is created, it is automatically protect by copyright, you may always get the permission of sharing and reusing their work.
Creative commons licenses elements:
-you must acknowledge the author and contain their work when you publish your work
-the author is the only person who can make money from their work
-you must get the permission before retouching or mixing up the original creation
Click here to view the more specific content about the licenses:
http://creativecommons.org/licenses/?lang=en