A trademark can be a symbol, word, phrase or device that identifies a company and is registered with the United States Trademark and Patent Office (USTPO). Once registered then the trademark is protected by trademark laws which work very similar to copyright laws. You can tell that a product is trademarked in that it will have the r with a circle around it or TM imprinted on the item or next to the name or slogan. Examples of trademarks are Jacuzzi which specifies the jacuzzi brand not all jetted tubs on the market. Another example is Xerox which refers to the brand not all copiers that are on the market. Companies work hard to protect their trademark names and may take legal action if they belive that they have experienced actual damages from someone using their trademark.