“Copyright © XXXX Big Business Inc. All rights reserved.”
Copyright is where one makes copies of what's on their right.
It could also mean the copy to make rights. Which one it means hasn't been resolved yet.
The semi-sensible explanation
Copyright is a law that gives creators who create creative works of creativity a monopoly over the copying of copies, the distribution of copies, and other such uses of their creative work. Copyright infringement is the term for violation of this monopoly. The usual penalty for copyright infringement is to pay the copyright holder a lot of bananas. So if you are very rich, you can do whatever you want, especially if you have wealthy lawyers. Just make sure that your lawyers are better paid and more numerous than those of the RIAA or MPAA. After all, the one with the most lawyers wins, as long as the lawyers are equally smart.
In the Untied Staetz, copyright lasts for the life of your mom plus 70 years. It gets worse: Copyright in the US is automatic even for unpublished works, and maybe even unworked publications. Unworklished pubs may also count. I dunno.
However, if the work is copyrighted outside of the United States, a public domain work can be pulled back into copyright in the Untied Staetz according to some guys with wigs.  This rule was made so that student bands and nonprofit orchestras will stop playing old stale music made by some guy that has been dead 70 years.