A copyright search is a search for who owns the rights to written, created or published materials such as books, music, art, periodicals, etc. Copyrighted material cannot be copied or used for profit without obtaining permission from the owner of the copyright.
When people create works of literature, music or art, they establish that it is unique and that they created it by filing for and obtaining a copyright. A copyright doesn't always necessarily stay with the original creator, however. Copyrights are frequently bought and sold. Once a copyright is sold, original owners no longer own the rights to that material, even though they may be the ones who created it. People who own copyrights are entitled to the royalties as detailed by copyright anytime that a work is used for public consumption.
The world's largest collection of copyrighted information is found at the United States Copyright Office. In a single year, the office processes about 700,000 copyright requests and claims. Copyrights do expire but the laws that dictate the expiration of a copyright vary by the filing date and the type of copyright. In general, the range is about 100 years, though some copyrights are valid for 70 years plus the author's life, which can potentially extend a copyright significantly beyond the 100-year mark.