Fair use is a doctrine in United States copyright law that allows limited use of copyrighted material without requiring permission from the rights holders, such as use for scholarship or review.

Because copyright law is essentially a law requiring you to circumvent common sense, it is required for another law to exist so lawyers don't maul you to death with their briefcases. This is when Fair Use comes in to tap the lawyers on the shoulder to roundhouse kick them in the face, Quentin Tarantino style.