In the United States, the idea for Copyright was embedded in the U.S. Constitution in Article 1, Section 8, which describes the powers of Congress.
"Congress shall have Power...To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries"
According to U.S. Copyright Law, copyright protects works of "original authorship that are fixed in a tangible expression". This includes broad categories of literary works, musical works, dramatic works, visual (pictorial, graphic, and sculptural) works, pantomime and choreographical works, motion pictures and other audiovisual works, sound recordings, and architectural works. Copyright takes effect immediately once a work has been fixed in a tangible form - registration is not necessary - and lasts for 70 years after the death of the author, or, in the case of works for hire or anonymous/pseudonymous works, 95 years from publication or 120 years from creation, whichever is shorter.
Copyright gives the author the following exclusive rights:
From "Copyright Basics"(pdf), U.S. Copyright Office Circular 1