1. Tú vs. Usted

2. Tú vs. Usted (Ud.) Both mean you
Tú (singular familiar) is used with people that you are familiar with or someone that you refer to by their first name.

3. Usted (Ud.) (singular formal) is used with a person who you should respect, for example a doctor, teacher, elder, or an unknown person.
Usted is also used with someone with the title Mr., Mrs., or Ms.
Usted is almost always abbreviated Ud. (In Spain it may say Vd.)
Usted is sometimes used with family members (parents and grandparents) to show a sign of respect.

4. Práctica Your best friend Your friend’s mom Your teacher Your brother
Someone you just met who is your age
Someone you just met who is older than you
Your grandpa

5. Respuestas Your best friend Tú Your friend’s mom Ud. Your teacher Ud.
Your brother Tú
Someone you just met who is your age Tú
Someone you just met who is older than you Ud.
Your grandpa Ud. / Tú