"Su" is formal. "Tu" is casual and also when it goes with accent (Tú) means you informal. hope it was of any help to you and good luck with your spanish! Adios n_n

Tú= you Tú eres inteligente =You are intelligent Tu=your Ese es tu carro= That is your car Su= her, his, their. Esa es su falda= That is her skirt. Ese es su carro=That is his car. Esa es su aldea=That is their village. Note: Su can be used as Tu as a form of respect for older people or strangers, or your parents.It is used for good manners and the phrase- Hablame de Tu- means you are allowed to use tu instead of su. Example: Disculpe ese es su carro? Excuse me is that your car? Sí pero no me hables de usted, hablame de tu.Yes but don't talk to me like -you-( as formal) talk to me like-you-(as informal) Ok entonces ese es tu carro? Ok then is that your car? puede moverlo? can you move it? ( this is a formal way like su) perdon... puedes moverlo? Sorry can you move it? ( this is informal way like tu)

Tu tiempo (your time) if it's informal. Su tiempo (your time) if it's formal Tú means "you" (Ex. You are nice) , don't get confused with those explanations above ;) just remember: TU: YOUR TÚ: YOU

Hi Hikari Tú (with written accent) = You , informal. For relatives and friends. But tu (without written accent) is a possessive pronoun = your . Su = Your , formal. For unknown people, your boss, etc. Regards María