what does 'this' mean in the sentence? I don't think it refers to distance or something.

Native speaker’s answer
Rebecca
We use 'this' to refer to someone who is unknown to the listener. Ex: I met this girl at the gym the other day. Her name is Mary and she is so cool. You've got to meet her someday. Ex: This random guy stopped me on the street and asked for my phone number! Of course, I said no because I'm married. I hope I never see him again!