The author expounds what educational technology is from four aspects: its definition, knowledge source, basic structure and research object. Keywords: educational technology; Definition; Sources of knowledge; Infrastructure; Research object 1. The definition of educational technology The classic definition of educational technology is the definition of educational communication and technology association. There are definitions of 1963, 1970, 1977,1994,2005. 11.AECT1963 defines audio-visual communication as a branch of educational theory and practice, which mainly studies the design and use of information that controls the learning process, including: (1) studying the unique relative advantages and disadvantages of image information and non-representation information that can be used for purposeful learning; (2) Use the personnel and equipment in the educational environment to organize and systematize information. These tasks include the planning, production, selection, management and application of the whole teaching system and its components. Its practical goal is to effectively use every communication method and media to develop learners' full potential. 2. Educational Technology Committee 1970 defines teaching technology as a systematic method to design, implement and evaluate the whole teaching and learning process according to specific goals. Based on the study of human learning and communication, it comprehensively utilizes human and material resources to achieve more effective teaching purposes. 3.Sillber defined teaching technology as the development (including research, design, production, support-supply and utilization) and management (including organization and personnel) of teaching system components (including information, personnel, materials, equipment, technology and environment) in a systematic way in 1970. Its purpose is to solve the problem of education. 4.AECT 1972 defines educational technology as a field that benefits human learning through the systematic identification, development, organization and utilization of all learning resources and the management of these processes. 5.AECT 1977 defines educational technology as a comprehensive organic process of analyzing problems and designing, implementing, evaluating and managing solutions to problems, which involves people, procedures, ideas, equipment and organizations and is related to all aspects of human learning. 6.AECT 1994 defines educational technology as the theory and practice of designing, developing, utilizing, managing and evaluating related processes and resources to promote learning. 7. In 2005, AECT defined educational technology as the study of the creation, utilization, management and moral practice of various appropriate technological processes and resources to promote learning and improve performance. From the definition of AECT, we can see that in 1960s and 1970s, teaching technology was regarded as a process. Starting from the definition of "94", educational technology does not know the process, which is a process and a resource. From the definition in 2005, it can be seen that the research object of educational technology is more and more clear, and it is the process and resource of research technology. Professor Li Kedong's definition of educational technology is that modern educational technology is the theory and practice of realizing teaching optimization by using modern educational theory and modern information technology through the design, development, utilization, management and evaluation of teaching and learning processes and resources. My definition of educational technology is: educational technology is to solve problems in education with technology, with the purpose of improving the quality of education, improving teaching efficiency and expanding the scale of education. Second, the knowledge source of educational technology In the fourth issue of Open Education Research in 2004, based on the orientation of educational technology and its disciplines advocated by the author, Liu Meifeng made an exploratory discussion on the knowledge source of educational technology from four aspects: the philosophical and cultural level, the scientific level, the practical experience of educational technology and its practical objects, which will affect the curriculum setting and orientation of educational technology specialty to some extent. At the same time, it also indicates the knowledge quality that an excellent team of educational technology researchers and practitioners should have. Third, the basic structure of educational technology On this issue, Zhang Jianwei mentioned in an article "The Basic Structure of Contemporary Educational Technology Research Field" published in "Educational Research" in 2002 that educational technology is the most independent applied discipline, and its research field can be divided into two levels: basic exploration and applied exploration. There are three main directions in basic exploration: teaching design research, innovative technology research and cultural research; At the level of application exploration, there are three closely related fields: IT integration and school education, performance technology and enterprise training, distance education and distance training. In 2006, the article "Educational technology is a systematic technology to solve educational problems" was published in Modern Educational Technology, in which Zhang vividly compared the field of educational technology with three cabinets. The front of the three cabinets in the picture shows the breadth of the field of educational technology, the drawers on the cabinets represent the sub-fields of educational technology, and the side of the cabinets symbolizes the depth of practice and research in this field. The model explains the specific research and practical activities of professionals in this field to achieve their goals, thus defining the scope of educational technology. Four. The research object of educational technology Educational technology and the research object of educational technology are important issues that must be discussed in educational technology. However, there are different opinions about what educational technology studies. Professor Jiao Jianli has made two online surveys on the research objects of educational technology. The survey results show that the research object of educational technology is still quite vague. Different people have different views on some common expressions of educational technology research objects. Jiao made a statistical analysis of the research objects of educational technology. The viewpoints of domestic educational technology research objects can be roughly divided into five forms: process and resources, law of phenomena, technology in education, application of educational media and methods, and technical problems. There are three main types of discussions about the research object of educational technology abroad: content theory, definition theory and task theory of description. Jiao's research conclusion is: Generally speaking, in the forest of educational science, educational technology mainly studies and solves educational problems by means of pursuing goals. Educational technology is more technical than scientific to solve these problems. This is the difference between educational technology and other branches of educational science. Professor Zhang Zuxin is also talking about technology. He believes that the purpose of educational technology is to solve educational problems and emphasizes that educational technology is technology. Some people in China call educational technology research and practice activities "audio-visual education" or "modern educational technology". Although the name is different, domestic academic circles have the same purpose of "improving education quality, improving teaching efficiency and expanding education scale". The meaning of this purpose is that there is a certain gap between the current goal and the development goal of education to measure its current situation, and the research and practice of educational technology (or audio-visual education) is to narrow the gap between the goal and the current situation. The gap is a contradiction and a problem that needs to be solved. Foreign educational technology documents often mention that educational technicians are "problem solvers", which embodies the purpose of this field. 5. Summary In the process of improving the teaching environment and teaching quality, educational technicians should always think about how to solve it with technology, otherwise it is not educational technology. I agree with the view that the research object of educational technology is the task theory of educational technology problems.