You may remember being taught in school that the French for ‘us’ is 'nous'. And then you may have been told that 'on' in French is the equivalent of 'one', as in, one is not amused. However, language changes and evolves and, whereas in English the use of the pronoun 'one' is quite unusual and possibly old-fashioned, 'on' in French has gained in popularity and now is used much more than ‘nous.
A reason for this increase in popularity is down, in part, to a laziness of French speakers. As ‘on’ has the same verb endings as ‘il/elle’, the verb also sounds the same as the ‘je’ and ’tu’ forms, thus the speaker has to think less about conjugating the verb. Here’s an example: je regarde, tu regardes, on regarde.
Another reason for its popularity is the fact that the meaning can be quite fluid. We can use ‘on’ to refer to people in general (where in English often say ‘you’). For example, on doit se tenir à droite – you must stay on the right. But ‘on’ could also refer to you, me and the others we were with – on s’est bien amusés hier soir – we had a great time last night. Lastly, ‘on’ is used in French where English would use a passive. For example, ‘French is spoken here’ is often translated as ‘ici on parle français’.
If you are lucky enough to go to France soon, listen to the people around you and you’ll hear lots of ‘on’. And then try using it – you’ll sound more French and will spend less time conjugating the verbs… which will lead to more fluent French…