This passage is an example of indirect characterization through dialogue.
Indirect characterization is the process in which an author describes the personality of a character in an indirect way, that is, through the use of dialogue or an action. Unlike direct characterization, indirect characterization is based on what a character does or says. In this case, it is the dialogue what allows the reader to identify Terrence as someone who is happy to see Pat but also worried about her. At the same time, the dialogue shows that Pat is sad and that something has happened to her since she does not show enthusiasm when replying to Terrence and uses few words to communicate with him.