First, some basics:
Вы [vy]. Here we look at the pronoun “Вы” in its singular form as at a formal polite pronoun; while Ты [ty] is used when talking to a friend or a person you know very well.
pronouns are written in lower case, unless they are at
the beginning of the sentence, of course.
So, we write the pronoun “I” – я [ya] in lower case, it's even considered impolite to write about yourself in a capital letter.
like with any rules, there
The 2nd person pronoun Вы and its variations in different cases, e.g., Вы, Вам, Ваш, Вами etc. are written in upper case if you write a letter to a person, one person (singular ). It’s considered polite to use in this case Вы with a capital В. And it doesn’t matter if it’s an official letter or a personal one.
When writing to a group of people вы is always written in lower case.
Where did "Вы" come from?
Вы came into the Russian language only in the 18th century from Western European languages and was the result of influence mainly of French and German languages. It all started with Peter the Great who was a huge fan of everything European and “cut a window through to Europe” as Pushkin said about him.
Before that it was traditional to use Tы pronoun when talking to the Tsar (King) or elders and even when praying to the God.
famous Dictionary of the Russian Language Vladimir
that the use of Вы was “a
Nevertheless starting from the 18th-century Вы became a generally accepted pronoun in Russian.