A trademark is a declaration of ownership of the intellectual property rights of a brand, expression or sign. A logo, a slogan or a particular pattern may all be trademarked.
The small "TM" denotes that the trademark is claimed but not registered. The small "R" in a circle means it has been registered with the United States Patent and Trade Office based on a bona fide intent to make use of the mark on a product or with a service offered to the public.
A trademark attorney in United States can help individuals or companies register their trademark or litigate a trademark violation.