A copyright is a form of intellectual property. Intellectual property is the legally protected right to an exclusive creation of the mind. Owners of intellectual property are granted exclusive rights to their patents, trademarks and copyrights, among other such property.
Copyright protection extends to the author of exclusive original works. These works include but are not limited to writings, music, plays, cinema, dance, or other original and exclusive art. The author is the creator of the original idea. An idea cannot be protected by a copyright as it is intangible, having no physical presence, but once that idea has been translated by the author into words, music, film, artwork, or other forms, it falls within the purview of the protection of copyright laws. There is no requirement for a person to seek actual copyright protection from the U.S. Copyright Office unless seeking to enforce a copyright. Translating the exclusive idea into a tangible form that is perceptible either directly or with the aid of a machine or device is all that is needed.
Rights of Registered Works
Some people wish to have their work registered with the U.S. Copyright Office for purposes of making a public record of the copyright and having a certificate of registration. Registration can also serve as evidence of the copyright in a court of law.
Copyrights are so old that they are recognized by the United States Constitution where it protects "by securing for limited Times, to Authors and Inventors the exclusive Right to their respective Writings and Discoveries." The "limited Times" to authors extends a lifetime plus 70 years or even longer, depending on the circumstances of authorship. Authorship is encouraged to perpetuate further creativity, expression, and development. The motivation for these ends comes of course, in the form money. How much money? Last year alone, Michael Jackson's copyrighted material brought the owners of the copyrights over $150 million. Elvis' copyrights brought in over $50 million.
The United States has copyright agreements with most countries, but not all. However, the person or entity seeking to enforce an international copyright is very well protected.