Salut !
"Tu" :
- people you are the closest to.
- Your parents, your husband/wife, your friends, maybe some of your colleagues...
These are people you can use “tu” with.
You never use “tu” when talking to a group.
"Vous" :
If you talk to several persons, you always use “vous”, because “vous” is also the plural “you”
You use “vous” to say “you” in French with:
People you don’t know (people in the street, sellers…)