Concept notes and resources redirects you to pages with understanding of concepts in form of documents, videos or external links. Some external links may point to resources from other service providers. The objective is just to help students find good material easily.
Practice problems are a set of posts that usually have some challenge/unsolved problems related to the given topic. They are advised to be solved by the student once the once he/she has practiced all the concept learning code sheets and solved problems in a topic and its previous topics.