A trademark marked TM (for example AlfaTM) is just a signal from the user of the trade mark that it is to be regarded as a trade mark and not as a firm's name, for example. Such a trade mark does not have any formal legal protection.
A trademark marked ® (for example Beta®) is a registered trade mark. Such a trade mark has legal protection through the trademark law of the country of registration. A registered trademark does not have this protection in countries where it has not been registered.