  In (D1) the word ‘Jim’ is used to talk about (or signify, or denote) a person, i.e. Jim, and the sentence says about that person that he went to Paris. In (D2) the word is not used in that way. Instead, ‘Jim’ is used to talk about (or signify or denote) a word, i.e. ‘Jim’, and the sentence says about that word that it has three  letters[5]. In (D1), ‘Jim’ is being used and in (D2) it is being mentioned.