If you have ever written something or created art, or if you have even looked at the front cover a book and seen that little copyright logo, you may wonder, what is copyright exactly? The answer is that copyright is a specific legal term, designed to create rights in something intangible.

The Dictionary defines copyright as:
the exclusive right to the publication, production, or sale of the rights to a literary, dramatic, musical, or artistic work, or to the use of a commercial print or label, granted by law for a specified period of time to an author, composer, artist, distributor, etc.: symbol ©
In other words, it is a type of legal protection that ensures that the owner -and only the owner- can publish, print or sell the work that he owns.
Copyright is protected in order to encourage productivity and creativity and to protect people's investment of time and energy. It is a type of ownership interest.
When you own something tangible, such as a piece of land or a piece of jewelry, you have the exclusive right to use and enjoy that item. If someone else takes it from you, you are no longer able to enjoy and possess it. As a result, the law protects your interest in that property. No one is allowed to come into your house and take your TV, your car, or anything else that belongs to you. If they do, they can be punished.
Things get a little trickier when it comes to copyright. After all, words on a page can't be physically stolen. You can't lock them up and prevent someone from walking away with them. Furthermore, if someone does take the words from a book, retypes them and reprints them, you will still have your original book.
However, if someone does take your work, retype it, reprint it and start selling it, the value of that work may diminish. You may not be able to sell your book (or piece of art, or song, or whatever else it is that you created) for as much money. You may not even be able to sell it at all.
As a result, copyright law was created in order to protect your interest in that intangible product -that art, that music- that you created using words, paint, and your talent. So, what is copyright law -it is legal protection for creative endeavors.
Copyright law protects any creative endeavor. However, it is distinct from patent law (which protects the rights to the invention of a tangible item, even if that item is never actually produced) and from trademark law (which protects distinguishing words, names, symbols or devices). It applies only to creative works or endeavors.
Furthermore, according to the United States Patent and Trademark Office, "The copyright protects the form of expression rather than the subject matter of the writing. For example, a description of a machine could be copyrighted, but this would only prevent others from copying the description; it would not prevent others from writing a description of their own or from making and using the machine."
Copyright only grants exclusive rights for a set period of time. The length of time a copyright extends for varies and has been changed several times since copyright law came into existence. You can find the exact term for specific items on the website of the US Copyright Office. For books, for example, the copyright period lasts for the life of the author plus 70 years. Different rules apply for different mediums, or for ghost written works.
When answering what is copyright protection, you also need to look at the limitations of copyright. While copyright prevents distribution or sales by anyone other than the author, there are certain limitations on a grant of a copyright.
The major limitation to copyrighted work is the fair use exception. Under fair use principles, some portions of a copyrighted work can be copied, as long as you have a legitimate reason for doing so. Although an exact definition of fair use isn't spelled out in copyright legislation, generally if you use small portions of a copyrighted work and you add to them, comment on them, criticize them, or otherwise use them for a legitimate purpose, you are not violating copyright law.