What is a copyright?
A copyright is the legal protection given in the United States to original works of authorship, including books, paintings, photos, music, video, software, and so forth. Copyright protection attaches to a work the moment it is fixed in tangible form (on paper, on video, and so forth) and prevents others from exploiting the work without permission.
Copyright is a bundle of rights
A copyright actually is a bundle of rights that includes the exclusive right to distribute, sell, duplicate, publicly perform, and create derivative works from the work. The length of copyright protection for older works is often difficult to determine, but for newer works these exclusive rights last at least 70 years, depending upon whether the author is a person or a company. The fact that a work is old doesn't necessarily mean that the copyright on it has expired. Until the end of the term of protection, a copyright owner has the right to sell, transfer, assign, or license one or all of his exclusive rights to someone else.
Selling versus giving away an item
Copyright protection includes the exclusive right to distribute or sell the copyright work. This usually means that giving away a copy of a copyrighted work (for example a copy of a videocassette) is not permitted. Thus, selling a pencil for $5.00, and including for "free" an unauthorized videocassette copy would probably be an infringement.
Copyright registrations and markings
In the United States, it is no longer necessary to register a copyright to enjoy copyright protection, although you may have to register your copyright if you want to file a legal action concerning your copyright. It is also no longer necessary to place a © on the copyrighted work, but it is a good idea to do so. The absence of a © doesn't mean its okay to copy, alter or sell the work without permission.
Resale of copyrighted works
Under the copyright laws, the owner of a particular copy of a copyrighted work is generally entitled to resell the particular copy they own. If you have licensed the right to use a particular copyrighted item, you should review the license and consult with your attorney to determine whether you can resell the item.
Rights of publicity
Similarly, the unauthorized commercial use or sale of someone's likeness (face or image), name, or signature on a product is prohibited by California's "Right of Publicity" law and some privacy laws. Thus, the commercial use of a photograph of a celebrity may violate that celebrity's right of publicity even if you took the picture yourself and own the copyright.