This article aims to review literature on feedback to teachers. Because research has hardly focused on feedback among teachers, the review's scope also includes feedback in classrooms. The review proposes that the effectiveness of feedback and feedback processes depend on the learning theory adhered to. Findings show that regardless of the learning theory effective feedback is goal- or task-directed, specific, and neutral. In addition, four rules of thumb were formulated that reflect what a majority of learning theories suggested as effective for learning. Finally, some feedback characteristics were considered effective from only one learning theory. The article shows that feedback processes are complicated and many variables influence and mediate the processes. Most reviewed studies did not investigate the whole feedback processes, and therefore, we suggest that future research is needed to further understand feedback. (Contains 5 tables and 4 figures.)