What do you mean by the difference between an oath of divorce regarding a past event, which takes effect if the reality of the matter is intended, and some statements in which divorce does not take effect even if the reality of the matter is intended?

If a man says to his wife, "By divorce, you did such and such," believing he is truthful in his oath, then his divorce does not take effect, even if she had not done that. However, if he swore falsely and intentionally, then his divorce has taken effect according to the majority of scholars.