In broad terms, a copyright identifies your ownership of images. On the T3i/600D, you can add your copyright information so that your name and other information is embedded into each image that you shoot. This copyright information can be a first step in proving your ownership of images that are used without your permission. For this and other reasons, I encourage you to enter your copyright information. You only have to enter it once for it to be used on all your images. Also, the copyright information appears only in the images metadata, and not on printed images.
TIP: To complete the copyright process, register your images with the United States Copyright Office. For more information, visit www.copyright.gov.