"Fair Use" is a provision in US copyright law that imposes limits and exceptions to the exclusive rights of authors / creators.
It means that you can use copyright-protected media without asking for permission if the following factors speak in favour of your proposed use:
1. the way you use it;
2. the nature of what you use;
3. how much of the original material you use;
4. whether your use will impact the market for the work.
(...and here is the letter of the law)
In practical terms, the determination whether a use is "fair" is a subjective one. However, there are some
Understanding Copyright
If you still have questions, contact Copyright and Digital Rights Management Department.