A chatterbot is a computer program for simulating conversation between a human and a machine. You input a question or statement of any kind, and the chatterbot replies, just as a person would (using its own version of logic!).
Can a computer think, or have feeling? No, it cant, but we can simulate it, and thus fooling the user that they are talking to a real person.
It is interesting seeing what people talk about in an IRC session. They are more open to conersation than to a real person. People are curious, they love to chat, they love to ask about your life. If your program can simulate a real person good enough, they could be able to talk to a computer for hours on end without knowing that they're talking to a computer.