Trademarks are "signs" or "logos", perhaps combining a designed image and some text, which identify a business or organisation.
Google's trademark (logo)
Registered trade marks are another form of Intellectual Property rights and are governed by separate legislation. The ® mark indicates that a logo, brand name or title have been registered as a trade mark. A company name followed by the capital letters TM as a superscript can also be claimed as an indicator of copyright.