The Virginia Business Litigation Blog
A trademark is a type of intellectual property that generally consists of a distinctive sign or indicator used to identify the originating source of the products associated with the trademark, so that consumers can distinguish the trademark owner’s products from those originating from other sources. Section 45 of the Trademark Act defines the term “trademark” as “any word, name, symbol, or device, or any combination thereof-
(1) used by a person, or
(2) which a person has a bona fide intention to use in commerce and applies to register on the principal register…,
to identify and distinguish his or her goods, including a unique product, from those manufactured or sold by others and to indicate the source of the goods, even if that source is unknown.” See 15 U.S.C. §1127. An example of a “word” mark would be TOSHIBA. There are also design marks, like Nike’s instantly recognizable Swoosh. Even a sound can constitute a trademark (for example, NBC’s “ding, dong, ding” chimes). If you own a trademark, no one else can use it if their use would confuse consumers. Trademarks are identified in commerce by the symbols ™ (indicating that the trademark has not been registered) and ® (for registered trademarks). 
While registration of trademarks is not required, owners of registered trademarks may commence legal proceedings for trademark infringement to prevent the unauthorized use of that trademark. Unregistered trademarks, known as “common law” trademarks, may also be enforced in court, but generally only within the geographical area within which it has been used or will be used. A federally registered trademark, on the other hand, provides nationwide protection.
The term “trademark” technically only applies when the product identified by the mark is a good. When the mark is applied to identify a service, it is known as a “service mark.” Another similar term is “trade dress,” which applies to a product’s total image and overall appearance.
Unlike patents, another form of intellectual property, trademarks can be renewed forever as long as they continue to be used in commerce.