I don't know if it actually puts a real person on the other side or if it takes things that people have typed in and tries to find the best match for a response. So say you type in "How are you?", the computer would search for something that a real person used earlier as an answer to that question and then puts it as a response. With probably millions of people using this it can build up quite a large database and eventually get really good at conversation. At least that's what I always thought, though earlier it might have been person to person just to built up responses. I'm not quite sure anyway.