Explain how the character changed from the beginning to the end of the book. (Harry Potter and the Chamber of Secrets) (bump)

Well, it depends what you mean. Physically, he has definitely changed. He has matured, and by the last book, he is considered an adult. He is no longer the innocent boy who lives with his aunt and uncle, but a hero known all over the world. He has also learned some new powers, that he never used in the first few books. Being able to read Voldemort's mind and emotions was a connection that was never seen in the wizarding world. As Harry grew up, plus Voldemort's return to power, the connection opens up, and they can pretty much read each other's minds.