Trademarks and service marks serve essentially the same purpose, but there are slight differences in how they're applied and communicated to your market. Both are administered by the United States Patent and Trademark Office. This agency processes registrations for trademarks as well as service marks. Registration isn't mandatory, but it provides additional legal protection in certain situations.
Trademarks and service marks may include words, phrases, symbols, images or devices that identify the source of an offer to a market. A trademark identifies the source of hard goods or tangible items, while a service mark identifies the source of services.
The U.S. Patent and Trademark Office uses the terminology "trademarks" and "marks" synonymously to refer to both trademarks and service marks. If you choose to assert your trademark or service mark with a symbol, you don't have to register it. You may use the symbol "TM" for a trademark or "SM" for a service mark. You can use the "®" symbol only if you have formally registered your mark and the PTO has granted your application.
You establish rights to trademarks and service marks by using them. Registration affords additional protection, but it doesn't guarantee that others won’t also use your mark. The best way to protect your marks is through a combined strategy of commercial use and registration; however, use alone establishes rights. You might use your marks in the packaging of goods, advertisements, promotions, branding and marketing materials or business communications, including letterheads, envelopes and invoices.
Use your marks in conjunction with what you are identifying. If there's not a clear nexus between the mark and your goods or services, you might not be satisfying the legal requirement to establish your rights. This can be somewhat trickier for service-based businesses. Avoiding confusion is important. If someone disputes your use of a mark, or if you dispute someone else's use of a mark you claim, it's always prudent to consult with an attorney experienced in trademark law.