Copyright is a set of exclusive rights granted to the author or creator of an original work. These rights include:

• reproduce the work
• prepare other works based upon the work ("derivative works")
• distribute copies of the work by sale or other transfer of ownership, or by lease
• perform the work publicly
• display the copyrighted work publicly

Under United States law, seven types of works can be copyrighted:

• literary works
• musical works
• dramatic works
• pantomimes and choreographic works
• pictorial, graphic, and sculptural works, including fabric designs
• motion pictures and other audiovisual works
• sound recordings

A "work" cannot be just an idea to qualify for copyright protection. It has to be original and be the result of at least some creativity. It must also be realized in a "fixed form."

The exclusive rights are however balanced for public interest purposes with limitations and exceptions to the exclusive right - such as fair dealing and fair use. Copyright theory says that it is the balance between the exclusive rights and the limitations and exceptions that engenders creativity. Copyright does not protect ideas, only their expression or fixation. In most jurisdictions copyright arises upon fixation and does not need to be registered. Copyright owners have the exclusive statutory right to exercise control over copying and other exploitation of the works for a specific period of time, after which the work is said to enter the public domain. Uses which are covered under limitations and exceptions to copyright, such as fair use, do not require permission from the copyright owner. All other uses require permission and copyright owners can license or permanently transfer or assign their exclusive rights to others.

Initially copyright law only applied to the copying of books. Over time other uses such as translations and derivative works were made subject to copyright and copyright now covers a wide range of works, including maps, dramatic works, paintings, photographs, sound recordings, motion pictures and computer programs.

Source: Wikipedia