A trademark is a word, phrase, symbol, or logo used to brand, identify, and distinguish a product. A service mark (or servicemark) is a word, phrase, symbol, or logo used to brand, identify, and recognize a service. The TM and SM designations are placed with trademarks and service marks to show that the owner has started the registration process. Both trademarks and service marks serve the purpose of protecting the brand and reputation of the mark holder and helping prevent others from using the same or similar marks for similar products or services. The legal requirements and processes for obtaining trademark or service mark protection are similar. However, the registration process may vary slightly for trademarks and service marks.
Further extensive analysis on the difference and impact of registering a Service mark vs a trademark can be accessed.