why se?

Question

Why is it 'como se llama' or 'como se llama usted' - not 'como te llama'?

Accepted Answer

Hola Alice
This is because using the informal you (tú) or the formal you (usted) means that you don't just swap from tú to usted, but it comes with changing the conjugation too and for verbs that are used with a pronoun, i.e reflexive verbs, you need to apply the correct pronoun there too. The verb llamarse is one of these reflexive verbs that is used with these pronouns, so you need:

Yo me llamo 
Tú te llamas
Él / Ella / Usted se llama
Nosotros nos llamamos
Vosotros os llamáis
Ellos / Ustedes se llaman

You can see here that each subject has a specific reflexive pronoun.
This lesson about reflexive verbs in the present will help you understand it a bit better. 
Saludos cordiales
Inma

Answer

this is because, 'como se llama usted' is formal and, 'como te llama' is not formal