This document discusses the use of comparative adjectives in English. It explains that we use "more + adjective + than" or "adjective + -er + than" to compare two things or people. It provides examples like "My car is more expensive than your car" and "I am older than my brother." The document also notes some common mistakes to avoid, such as using "more taller" instead of just "taller" and forgetting to include the second element after "than" in a comparison.