Can be drawn on a plane, any two sides have no other intersection except the endpoint. Such a figure is called a plan, but some figures have intersections on the surface. As long as the drawing method is changed, there will be no intersections. Such a figure is also a plan. A five-pointed star with five vertices is a plan. As you said, the five-pointed star and the five-pointed star should be isomorphic, while the five-pointed star is a plan. What the book says may not be a five-pointed star but a complete figure with five vertices, that is, a figure embedded with a five-pointed star, not a plan.

Discrete mathematics:

Discrete mathematics is a mathematical discipline that studies the structure and relationship of discrete quantities and an important branch of modern mathematics. The meaning of discreteness refers to different connecting elements. The structure based on discreteness and the relationship between them are mainly studied, and its objects are generally finite or countable elements. Discrete mathematics is widely used in various disciplines, especially in the field of computer science and technology. At the same time, discrete mathematics is also a necessary prerequisite for many professional courses of computer specialty, such as programming language, data structure, operating system, compilation technology, artificial intelligence, database, algorithm design and analysis, theoretical computer science foundation and so on. Through the study of discrete mathematics, we can not only master the descriptive tools and methods for dealing with discrete structures, but also create conditions for subsequent courses, improve abstract thinking and strict logical reasoning ability, and lay a solid foundation for participating in innovative research and development in the future.