A trademark is a word, phrase, symbol or design, or a combination of words, phrases, symbols or designs, that identifies and distinguishes the source of the goods of one party from those of others.
A service mark is the same as a trademark, except that it identifies and distinguishes the source of a service rather than a product.
A registered trademark is designated by a ® while an unregistered claim to a mark is made by using the TM or SM designations.