To sum up, there are two main viewpoints: the first viewpoint defines teaching theory as knowledge system or cognitive system. For example, some scholars define teaching theory as a systematic theoretical understanding of teaching activities, which is a knowledge system expressed by people with the help of a series of concepts, judgments and reasoning. Some scholars pointed out that educational theory (including teaching theory) as a noun refers to people's theoretical understanding of education (teaching). The so-called theoretical understanding refers to the result of a kind of understanding and the product of rational thinking, with the common characteristics of generalization and abstract judgment (different degrees), and the differences between the levels and types of generalization and abstraction constitute its internal levels and types. Some scholars also believe that teaching theory is the product of rational thinking on teaching practice, and it is a hierarchical and complex cognitive system that can guide teaching practice by actively reflecting teaching phenomena and their contradictory movements. The second view regards teaching theory as teaching theory and defines it as a branch of pedagogy. It holds that teaching theory is a subject that studies teachers' behavior of guiding, maintaining or promoting students' learning in teaching situations, constructs a universal interpretation framework, and provides general provisions or prescriptions to guide classroom practice.