Many mathematical objects, such as numbers, functions, geometry, etc. A that reflects the internal structure defined for continuous operations or relationships. Mathematics studies the properties of these structures, for example, number theory studies how integers are represented under arithmetic operations. In addition, things with similar properties often occur in different structures, which makes it possible to describe the state of a class of structures through further abstraction and then axioms. What needs to be studied is to find out the structures that satisfy these axioms among all structures. Therefore, we can learn from abstract systems such as groups, rings and fields. These studies (defined by algebraic operations) can form the field of abstract algebra. Because abstract algebra has great universality, it can often be applied to some seemingly unrelated problems, such as some old problems of drawing rulers, which are finally solved by Galois theory. It involves field theory and group theory. Another example of algebraic theory is linear algebra, which makes a general study of vector space with quantitative and directional elements. These phenomena show that geometry and algebra, which were originally considered irrelevant, actually have a strong correlation. Combinatorial mathematics studies the methods of enumerating digital objects satisfying a given structure.