A trademark is a word, phrase, symbol, and/or design that identifies and distinguishes the source of the goods of one party from those of others. A service mark is a word, phrase, symbol, and/or design that identifies and distinguishes the source of a service rather than goods. The term “trademark” is often used to refer to both trademarks and service marks. The registration has several advantages, including a notice to the public of the registrant's claim of ownership of the mark, a legal presumption of ownership nationwide, and the exclusive right to use the mark on or in connection with the goods or services set forth in the registration.
A trade mark protects the identity of your goods and services. Once you register a trade mark, you have the legal right to use, license or sell it within the USA for the goods and services for which it is registered. You also have the right to prevent others from using it.
If you do not register, another party could register your brand as a trade mark and you could be forced to defend your rights - you may even need to rebrand.