Dynkin diagrams are graphical representations used to classify simple Lie algebras and their associated root systems. Each diagram consists of nodes and edges, where nodes represent the simple roots of the algebra, and edges indicate the angles between them. The diagrams help visualize the relationships and structures within the algebra. These diagrams are named after Eugene Dynkin, who introduced them in the 1940s. There are several types of Dynkin diagrams, including A, B, C, D, and exceptional types like E and F. They play a crucial role in various areas of mathematics and theoretical physics, particularly in the study of symmetry and group theory.