Tu vs Vous
Addressing someone with vous shows respect toward them. You can use tu with friends, fellow students and immediate family members, but for everyone else use vous, at least in the beginning. Generally you should ask for permission before you begin to address someone with tu ( tutoyer quelqu'un).
Je peux vous tutoyer ?
Vous is also used as plural 'you'.
|-Vous venez quand?
-Robert et toi.
|-When are you coming?
-Robert and you.
On is a pronoun which is often used to represent people in a general sense.
|Quand on a tout, on est trop plein. -Joseph
When you have everything, you are too full (satisfied).
On a souvent besoin d'un coup de main --rarement d'un coup de
It also can be used to create a passive sentence. Technically it's not a passive sentence because on acts as the subject, however because the perpetrator is not mentioned it is passive sentence in spirit.
|On a bu tout le vin.
All the wine was drunken.
It also is used to say 'we' in an indirect way.
|On mange maintenant ou on regarde le film d'abord ?
We eat now or watch the film first?
Normally in written French, on becomes l'on when it follows et or a word ending in a vowel.
|Quand on n'a pas ce que l'on aime, il faut aimer ce que l'on
-- Roger de Bussy-Rabutin
When you don't have what you love, you must love what you have.
Representing the Non-living
While the third person subject pronouns normally are used to represent the living, they also can represent the non-living. By 'non-living' I don't just mean mummies, ghosts or corpses; I also mean any object: books, houses, chairs, etc.
J'aime ce village. Il est très petit.
J'aime cette ville. Elle est très petite.