Modes of address: and usted

Castilian Spanish has four different ways of translating 'you'!

you - familiar 2nd person singular of verb
usted you - polite 3rd person singular of verb
vosotros,-as (all of) you - familiar 2nd person plural of verb
ustedes (all of) you - polite 3rd person plural of verb

 

e.g

Hablas espa˝ol? - Do you speak Spanish? (to a friend)

Habla usted inglÚs? - Do you speak English? (to a stranger)

A quick rule of thumb: if you would use someone's first name when addressing them, use  t˙/vosotros,-as; if you would use someone's surname, use usted/ustedes.