Tú and usted both mean you, so what's the difference? Tú is used in friendly conversations, while usted is for more formal interactions.
¿Cómo te llamas? is used to ask What's your name? in informal interactions. It literally means How do you call yourself?
Remember to use usted in more formal settings or when speaking to someone older than you.
Use estar to describe things that are temporary. For example, you would use estoy, estás, or está to talk about how people are feeling or doing.
Use ser for more permanent descriptions. For example, you would use soy, eres, or es to explain what someone is like or where they're from.