In singular number, 'tu' is used to address a family member, a friend, or a younger and known person .
'você' is used for formal relations .
In plural form 'vós' is used for family members, friends, or younger persons.
'vocês' is used to address many persons formally.
In Brazil 'tu' and 'vós' are not used. Instead 'você' and 'vocês' replace them.
In Portugal the term 'vós' is becoming extinct and is being replaced by 'vocês'. However it is used in classical literature and in most of the northen parts of Portugal.