could you please explain when we use if and when unless

If is used in the conditional clauses. (type 1,2,3 and 0) If you ask me ,I will help you. (1) If you asked me, I would help you. (2) If you had asked me ,I would have helped you. (3) Ask me, I will help you. (0) Unless is negative form of If. Unless =if + not Unless you ask me, I won't help you.