E-commerce is a constantly evolving concept. Throughout its inception and development, it has gradually formed unique and related key concepts. Mastering the basic concepts, definitions, and foundational knowledge of e-commerce is an important aspect of studying it. Additionally, e-commerce involves multiple entities using e-commerce application systems to conduct business activities. Modeling and analyzing this process is a crucial research approach to understanding its essence. In addition, research on recommendation systems is a distinctive area of study within the field of e-commerce and has played a significant role in driving its rapid development. This chapter primarily analyzes the basic definitions and models of e-commerce and introduces the recommendation system research.