The lay theory refers to the general knowledge constructs formed by individuals based on daily observations and personal experiences, as opposed to scientific explanations. It plays a crucial role in everyday life by helping people understand and explain phenomena around them, as well as guiding their decision-making and behavior. First, this paper defines the connotations of the lay theory, clarifies its distinctions from metaphor, schema, and stereotype, and systematically summarizes the manipulation and measurement methods associated with the lay theory. Second, this paper delves deeply into three significant themes: product quality, medical health, and consumer happiness, so as to provide a comprehensive overview of the effects of the lay theory from a marketing perspective. Third, this paper explores the process of invoking the lay theory, highlighting the critical roles of information accessibility, diagnosability, and applicability within this process. Based on the above discussions, this paper presents future prospects that include focusing on external environmental changes, advancing research at the group level, enhancing applications in the field of algorithms, and optimizing measurement methods. These prospects aim to further deepen our understanding on the role of the lay theory in the marketing field and provide guidance for research and practice in related fields.