"Copyright is a form of legal protection that provides authors of original creative works with limited control over the reproduction and distribution of their work." --April Hathcock
Copyright is a way to balance the rights of the creator with the public good over the control of intellectual property.
Under copyright law, creators have the exclusive rights to reproduce and distribute their work as they see fit for a period of time. Then, the work is released into the public domain; where anyone can use, adapt, or reproduce the work without getting permission or paying a fee.