When learning the German pronouns, note that:
The German pronoun "ich" does not start with a capital letter, unlike its English equivalent "I".
The third person pronouns "er", "sie" and "es" can refer to persons. However they also substitute for all masculine, feminine and neuter nouns respectively, regardless of whether they are persons or things.
Note that the pronoun "sie" can either mean "she" or "they" depending on context. And when it begins with a capital letter "Sie" is the formal form of "you"! Be very careful how you use this pronoun.
Sie or du?
The familiar or informal form "du" is used when talking to relatives, close friends and children.
It does not start with a capital letter.
The plural of "du" is "ihr".
The formal form "Sie" is used when you need to be more polite.
It is the usual form of address when talking to an adult whom you don't know well or at all.
A child would always say "Sie" to an adult outside his or her own family.
"Sie" always starts with a capital letter.
The plural form of "Sie" is also "Sie".
