What Is Fair Use?
Fair use is a doctrine under copyright law that permits the use of a copyrighted work under certain circumstances.
While citation and proper attribution protect against plagiarism, fair use protects against copyright infringement - both are important to be aware of when you're using someone else's work.
For more information, check out our Copyright and Fair Use guide.
Some Copyright Basics
Copyright protects original work - i.e. "literary, dramatic, musical, and artistic works" (US Copyright Office). It does not protect facts or ideas.
The creator of a work has copyright over the work the moment it is created, even if it is not registered with the US Copyright Office. You will have to register your work to file a lawsuit against another person or group for infringing your copyright, however.