Common law copyright is the legal doctrine that contends that copyright is a natural right and creators have the same inherent right to it as they would tangible property. The doctrine has been repudiated by the courts in the United Kingdom (Donaldson v. Beckett) and the United States (Wheaton v. Peters). In both countries, the courts have found that copyright is a limited right created by the legislature under statutes and subject to conditions and terms the legislature sees fit. The proponents of this doctrine contended that creators had a perpetual right to control publication of their work. While the legislature could grant such a perpetual right--in the U.K., Parliament has done so in regards to Peter Pan--it is under no obligation to and can set a limited term.
Copyright is not rocket science, and you should understand that it is your stock-in-trade, the core of your livelihood.
Under the 1976 Act, copyright is automatic when the work is created, and a work is "created" when it is fixed in a copy or recorded for the first time (e.g., the instant you lift pen from paper or your word processing software saves to disk).
A copyright is personal property and may be transferred by gift or for a fee, and may be bequeathed by will or pass as personal property by the applicable state laws of intestate succession.
Copyrighted works replicated onto digital media are easily and trivially copied via file sharing, and those who do this routinely break copyrightlaws hundreds or thousands of times, typically with minimal thought or concern.
Copyright concepts are perceived to be under challenge in the modern technological era, from the increasing use of peer to peer filesharing, to the downward trend in profits for major record labels and the movie industry.
Once the term of a copyright has expired, the formerly copyrighted work enters the public domain and may be freely used or exploited by anyone, as courts in the United States and the United Kingdom have rejected the doctrine of a commonlawcopyright.