Copyright protects original creative expression once it has been "fixed in a tangible medium" (e.g. recorded, printed, painted etc).
Licensing means you retain the copyright on a work and rent it to another party for a fee under contract.
Fair Use allows the public to use copyrighted material without asking permission for commentary and criticism, such as quoting material in a research paper or writing a film review.
Public Domain refers to creative works that are not, or are no longer, protected by copyright, trademark or patent law. No permission is required to use these works. No one may take a public domain work and copyright or trademark it.