1. Internal institutions: Internal institutions are institutions or departments established in schools or educational institutions to provide specific support and services. Internal institutions are usually directly subordinate to the management of the school and run by the faculty and staff of the school. Common internal institutions include educational administration department (such as academic affairs office, student affairs office and enrollment office), financial department, administrative department and student service center. The responsibility of the internal organization is to ensure the normal operation of the school and the learning environment of the students.

2. Teaching auxiliary institutions: Teaching auxiliary institutions are institutions that provide educational auxiliary services. Usually independent of schools or educational institutions, but in cooperation with schools. The goal of teaching aid institutions is to provide students with additional educational support to supplement their studies in regular schools. Auxiliary teaching institutions can provide extracurricular counseling, training courses, preparation and other services. They are usually composed of professional teachers or educational experts, and charge tuition or service fees. Mechanism is a component system formed by two or more components through movable connection, which can be divided into planar mechanism and spatial mechanism; According to the types of kinematic pairs, it can be divided into low pair mechanism and high pair mechanism; According to the structural characteristics, it can be divided into linkage mechanism and gear mechanism. According to the characteristics of the converted motion or force, it can be divided into uniform and non-uniform rotation mechanisms, linear motion mechanisms and so on. According to the function, it can be divided into safety insurance mechanism and interlocking mechanism. The mechanism is located in the kinematic chain. If one of the components is fixed and becomes a frame, the kinematic chain becomes a mechanism.