The United States Patent Office defines a trademark as:
...a word, phrase, symbol, design or a combination of words, phrases, symbols or designs that identifies and distinguishes the source of goods of one party from those of another.
A service mark is essentially the same but it is applied to a service rather than a product.
Trademarks/service marks do not have to be registered with a state or federal government to be valid, but they must be actively in use. The rules, governing a mark and its use in other countries varies. Some countries require a mark to be registered to be valid. A US trademark does not necessarily confer protection elsewhere in the world. Where a trademark/service mark is registered depends on where the goods and/or services are being marketed.
In the U.S. TM or SM indicates that a mark is being used by a company but is not registered, only when a ® appears has a mark been registered with the federal government. Unlike a patent or a copyright, a federally-registered trademark/service mark can last indefinitely if the owner continues to use the mark on or in connection with the goods and/or services in the registration and files all necessary documentation with the USPTO, etc. at the appropriate times. A trademark or service mark can be registered at both a state and a federal level.
Trade Dress refers to “a product's physical appearance, including its size, shape, color, design, and texture. … trade dress may also refer to the manner in which a product is packaged, wrapped, labeled, presented, promoted, or advertised, including the use of distinctive graphics, configurations, and marketing strategies.” Basically how a product is packaged. It does not need to be registered to have legal standing, as long as the packaging is distinctive enough. In some countries it is included as part of the trademark itself, in others it is separate. Trade Dress is increasingly coming into play with the advent of the Internet and webpage design.
eSearch plus. (European Union Intellectual Properties Office) Search trademarks, designs, mark owners and representatives, etc.
Register Your Trademark or Service Mark in Ohio. (Ohio Secretary of State) Guide to registering a trade/service mark in the state of Ohio.
Search by Business Name – Trademark/Service Mark Search. (Ohio Secretary of State) Can search by mark number, description or registrant name. Can also limit search results by status of the mark.
Trademarks - Trademark Electric Search System. (United States Patent and Trademark Office) Search engine for the USPTO database of registered trademarks, etc.
Trademark/Service Mark Searching - Other States. (United States Patent and Trademark Office) Contacts for each state. Some states have online databases available for searching, otherwise check with the state agency who handles trademarks, etc. about search options.
US Trademark Searching (United States Patent and Trademark Office) Search tips, etc. for conducting a trademark search
Form 555. (Ohio Secretary of State) Form for registering a trademark or service mark in the state of Ohio.
Index of all TEAS Forms. (United States Patent and Trademark Office) List and links to the various forms for filing, using, etc. a trademark.
Trademarks - Apply Now. (European Union Intellectual Property Office) Forms.
Trademark/Service Mark Searching - Other States. (United States Patent and Trademark Office) Contacts for each state. Some states allow online application, otherwise check with the state agency who handles trademarks, etc. about search options.
International Trademarks and Copyrights: Enforcement and Management. John T. Masterson, Jr. Chicago, Illinois: Section of International Law and Practice, American Bar Association, 2004. [tangible] [online] Provides practical advice on managing and enforcing trademarks and copyrights internationally.
Internet Intermediaries and Trade Mark Rights. Althaf Marsoof. Abingdon, England; New York, New York: Routledge, Taylor & Francis Group, 2019. Discusses the impact the internet has had on trademark enforcement and the gaps in existing tradition remedies to handle infringement issues under English law. Touches on how the U.S. and Europe are handling this problem.
Legal Dictionary - Service Mark. (The Free Dictionary by Farlex) Explanation of what a service mark is, how it is used, protections afforded by it, etc.
Register Your Trademark or Service Mark in Ohio. (Ohio Secretary of State) Guide to registering a trade/service mark in the state of Ohio.
Legal Dictionary - Trade Dress. (The Free Dictionary by Farlex) Explanation of what a trade dress is, how it is used, protections afforded by it, etc.
Trade Dress -- The Forgotten Trademark Right. (FindLaw. Robert B. Golden) Definition of trade dress with selected case law examples to help explain this often overlooked form of Intellectual Property.
Trademark. (Citizen Media Law Project) Although some of the material may be dated, this website provides a good general explanation of what a trademark is and what it protects against.
Trademark Basics. (United States Patent and Trademark Office) Information on trademarks, the process of filing, and what steps are necessary to file.
Trademarks Basics Fact Sheets. (INTA - International Trademark Association) Although most of the factsheets are restricted, there are unrestricted ones covering various topics on selecting and registering a trademark.
What is Trade Dress? (NOLO) Brief explanation of what is trade dress is and is not.
Wikipedia Encyclopedia - Service Mark. (The Free Dictionary by Farlex) Explanation of what a service mark is and how it is used. Includes references which can provide further information on the topic.