In German there are three words for ‘you‘: the familiar forms du and ihr, and the polite form Sie.
When talking to family, friends and small children, we use du to address one person and ihr to address more than one person.
When talking to people we do not know or don’t know well, we usually use the formal pronoun Sie to address one or more people. However, conventions are changing. When in doubt, it is always safer to use the formal Sie.
Please note that formal Sie is always written with a capital letter.