In my personal point of view, "on"(en français) is generally referred to "one"(in English). Sometimes, in informal occasions, it could also mean "nous" or "tu". For instance,
On se dit "tu"?, which literally means "Can we use 'tu' to address each other?"
On va aller au cinema ce soir?, which literally means "Are you going to go to the cinema this evening?" [I am not fully sure of this example, but I think that one may say it in such way.]
If you try to describe a matter that involves an impersonal subject pronoun or like “someone” in French, then we use "on" instead of "nous". Also, to express in passive voice, French prefers to use "on" instead (or in active voice with a reflexive verb). For instance,
On parle français ici. = French is spoken here. (e.g. in Quebec, Canada region)
On the other hand, if the subject matter strongly involves "you and me (us)" or "tu" (informal you), then in such cases "nous" or "tu" is preferred to be used, respectively.
Anyway, it would be nice if there could be any native speakers who may confirm (or rectify in case of mistakes) the above presumptions.
ciao ciao :)