The article discusses 13 patterns that make explanations hard to understand, including making outdated assumptions about the audience's knowledge, having inconsistent expectations of the reader's knowledge, and using strained analogies. The author argues that being aware of these patterns can help writers avoid them and make their explanations clearer. The article also provides examples of how to improve explanations, such as using implicit metaphors and providing realistic examples. By recognizing and avoiding these patterns, writers can create more effective and engaging explanations.