What's the differences between "must"& "have to"?

What do you think about Harry Potter? Up to you!!!!!!! ( Personal ideas. )

First notebook entry: Introducing myself Hello! My name is Valentine. I am a Thai student. Do you know Thailand like? If you don't know about my country, you can ask me. Now I learn in school. English Program. And I want to learn a foreign language will be more. A friend of mine recommended that I come to this site. If you want to use their language to foreigners. Thanks in advance for everything. Much love. ♥ Valentine.