The symbol TM is used to provide notice of a claim of common-law rights in a trademark. A TM usually is used in connection with an unregistered mark, to inform potential infringers that a term, slogan, logo or other indicator is being claimed as a trademark. Use of the TM symbol does not guarantee that the owner’s mark will be protected under trademark laws. The owner may continue to use TM should registration of the mark be refused.

Reference: International Trademark Association