Basic definitions:

Excerpts from Circular 1: COPYRIGHT BASICS

from the U.S. Copyright Office

April 1999 -- http://lcweb.loc.gov/copyright/circs/circ1.html#wwp

WHAT WORKS ARE PROTECTED

Copyright protects "original works of authorship" that are fixed in a tangible form of expression. The fixation need not be directly perceptible so long as it may be communicated with the aid of a machine or device. Copyrightable works include the following categories:

(1) literary works;

(2) musical works, including any accompanying words

(3) dramatic works, including any accompanying music

(4) pantomimes and choreographic works

(5) pictorial, graphic, and sculptural works

(6) motion pictures and other audiovisual works

(7) sound recordings

(8) architectural works

These categories should be viewed broadly. For example, computer programs and most "compilations" may be registered as "literary works"; maps and architectural plans may be registered as "pictorial, graphic, and sculptural works."