In this review of studies an answer is looked for the questions of the title, and an attempt is made to construct a system of integrative knowledge which can be utilized to benefit student teachers in their studies as well as teachers in their life-long learning. The teacher's practical theory is a scattered and non-uniform concept in educational studies. The teacher's beliefs is a wide construct which, in addition to the practical theory, contains self-efficacy, i.e., a motivational aspect. So far, the research has analyzed the sources of the teacher’s self-efficacy but also its connection to the teacher’s way of thinking, emotions, quality of the teaching, and the pupil's acting and learning. Emotions are an essential power in improving the quality of teaching and the student-teacher interaction. In summary, the teacher's practical theory, self-efficacy and emotions are essential research themes in educational research, but usually they have been studied separately from each other. However, in the past few years there have appeared studies which have managed to incorporate emotion and self-efficacy in the same research. In practice, a teacher has to function as a whole person and has to take into consideration the challenges of the context, so the need for more integrative research designs will be growing.