The appeal to emotion is only fallacious when the emotions that are elicited are irrelevant to evaluating the truth of the conclusion and serve to distract from rational consideration of relevant premises or information. For instance, if a student says "If I fail this paper I will lose my scholarship. It's not plagiarized" the emotions elicited by the first statement are not relevant to establishing whether the paper was plagiarized. On the other hand, "Look at the suffering children. We must do more for refugees." is not uncontroversially fallacious, because the suffering of the children and our emotional perception of the badness of suffering may be relevant to the conclusion. To be sure, the proper role for emotion in moral reasoning is a contested issue in ethics, but the charge of "appeal to emotion" often cannot be made without begging the question against theories of moral cognition that reserve a role for emotion in moral reasoning.
Appeals to emotion are intended to draw inward feelings such as fear, pity, and joy from the recipient of the information with the end goal of convincing them that the statements being presented in the fallacious argument are true or false, resp.