Remember that a dialogue is a technique used by writers in which teo or more characters are engaged in a conversation with one another. In this case, it's between the narrator (we can know that because he uses "I interruped") and another character named Robinson. By using dialogues, the story becomes lively and enjoyable as it makes the reader feel part of the it, it's like witnessing it in real time. The conversations between characters can tell us a lot about their presonalities and purposes. By using dialogues and a narrative technique, we can know the inner thoughts of some characters and therefore their hidden motive as sometimes what they think doesn't match to what they say.
As you can see, here the author already gave us the name of one of the characters and has set up a problem.
