<em>"Usted</em>" is the formal form of saying "You."
<em>"Tú" </em>is the informal form of saying "You
While "Tú " and "Usted" both mean "You", they convey the formality of a relationship.
<h2><u>Tu</u></h2>
<u><em>"Tú"</em></u>is mainly used when talking to friends, classmates, children, some family members and when there is a relationship of trust.
ex) (talking to your friend) Carlos ¿cuándo es tu cumpleaños?(Carlos, when is your birthday)
<h2><u>Usted</u></h2>
<u><em>"Usted" </em></u> is a more respectful and formal way of saying "You." It is mainly used when talking to someone older, teachers, and bosses. Some people substitute <em>"Usted</em>" with Señor( sir, Mr.) or Señora (Mrs.)
ex) (talking to a teacher) Señor Taylor, ¿cuándo es su cumpleaños? (Mr.Taylor, when is your birthday?)