Creative Commons materials have a license attached to them which clearly states conditions of use. Creative Commons (CC) is a global non profit organisation which was set up to "enable sharing and reuse of creativity and knowledge through the provision of free legal tools" (Creative Commons, 2016).
You can use CC materials under terms of the CC license (there are six core licenses that have slightly different, yet easily understood, terms). You can also apply a CC License to your own work: this will allow others to use your work under conditions that you choose.
Read more about finding Creative Commons materials on our Creative Commons Library Guide.
Public Domain materials refers to material in which all copyright has expired. This means that the material in its original format can be used by anyone for any purpose. Be aware that republication of material in a print or online format will mean that copyright may exist for the publisher for 25 years under the terms of topographical copyright.
For example, A newly published book on the complete works of Shakespeare: although Shakespeare's work is in the public domain, the new book would have copyright of 25 years on it, to protect the publisher's time and effort in producing the book.
When using online public domain sites, always check the terms and conditions of use as these may vary from site to site.
Balcomb, Ken. A humpback tail. Photo from National Oceanic and Atmospheric Adminstration Photo Library. Retrieved from http://www.photolib.noaa.gov/htmls/sanc0114.htm