English has one you. French has two, and choosing between them is a small social decision you'll make every day:

	tu	vous
Who	a friend, family, a child, a pet	someone you don't know, an older person, staff in a shop or café
How many	always one person	one person (politely) or any group
“And you?”	Et toi ?	Et vous ?
“How are you?”	Ça va ?	Comment allez-vous ?

A safe rule: start with vous with any adult you don't know. Among young people and friends, tu comes quickly. Someone may invite you to switch: On peut se tutoyer ? — Shall we say tu?