"A word mark is a type of trademark where the trademark owner is only claiming rights in the word, letters, numbers or slogans themselves, without claiming any right in the way those words are presented. In other words, there is no design or logo associated with the mark. Trademark protection of a word mark provides broader protection than a trademarked logo incorporating those words, because all appearances and use of the words are protected."

http://www.quizlaw.com/trademarks/what_is_a_word_mark.php