Creative Commons Licenses allow you indicate to the public what kinds of uses you allow for your copyrighted work. They are not an alternative to copyright; they work alongside copyright and enable you to modify your copyright terms to best suit your needs. You can ask that others who use your work simply attribute your work, you can restrict use to non-commercial purposes, or you can allow or deny derivatives of your work. You can also specify that anyone who uses your work must in turn license their own work in the same way.
Read more on the Creative Commons website: http://creativecommons.org.
When you upload your thesis or dissertation you will have the option of applying a creative commons license to your work.