Tu s’utilises avec des copains, des amis, des enfants, la famille.
Vous s’emmploi avec les personnes agées, l’administration, des inconnus,, des clients

You use Tu with pals, friends, relatives, children
and Vous with the others
old persons, the administration, unknown people, customers, people in the street . and with Donald Trump. At least personally I woudd’t say TU too D Trump.

same thing in in German with Du vs Sie
or In Italian where the “Vous” is ” Lei”

One easy rule of thumb: when in doubt, use “vous.”
You say “tu” to your friends, usually your parents (although I have known people who say vous to their parents) and close relatives, children and pets, and vous to everyone else.