Copyright ensures that the person who created something--whether a book or a piece of music--is reimbursed for his or her intellectual work. If there were no copyright protection, there would be no economic incentive to create these works.

A copyright is a set of legal rights that an author has over his work for a limited period of time. Copyright covers everything from using images or sound files from the Web to photocopying.

Most information is protected by copyright. The exception is work that is in the "public domain, " which can be reproduced or used by anyone. However, you still must credit the author. Some examples of public domain sources:

Public Domain Sources	Examples
Publications of the U.S. Government	U.S. laws and other publications of the Federal government, such as the U.S. Constitution
Copyright has been waived by the author	Software called freeware
Works on which the copyright has expired	Works by William Shakespeare