In addition to being used as an informal substitute for "nous," very often in the spoken language, the word "on" is often used in impersonal expressions as in the following examples: Il a 30 ans ? On dirait un ado ! He's 30 years old? One would think (he were) a teenager! On m'a dit que la réunion a été annulée. I was told (someone told me) that the meeting has been canceled. Si on veut, on peut. If one wants (to do something), one can (do that thing). J’étais né presque mourant ; on espérait peu de me conserver. (Rousseau) I was born almost dying: one (they) had little hope of saving me. Generally, one can translated this usage by "someone," "one," or "they" in English. Hope that helps!

ON - spoken french NOUS - written :P

@Fabrice Thank you for your addition explanation.

Great explantation, Brian. Congratulations. Just a question. I would have translated the « on » in French by « you » in American English. I was said that « one » is barely used in American English (whereas usual in British English=. So I am a bit surprised by your example : •Si on veut, on peut. If one wants (to do something), one can (do that thing). I would have said : If you want (to do something), you can (do something).