Teachers' beliefs are mental constructs that guide their thinking and behavior in the classroom. A belief is defined as a proposition that is accepted as true by an individual, even if they recognize others may hold different beliefs. Beliefs can be conscious or unconscious and serve as guides for thought and action. Research has explored how teachers' pedagogical beliefs influence their classroom practices and how teacher training programs impact teachers' beliefs. Considering whether studies clearly distinguish between beliefs and knowledge, and between espoused and enacted beliefs is important when reviewing research on teacher cognition.