It's a versatile phrase, and its exact meaning can vary depending on the context:
* "One can" (general possibility): "On peut aller au cinéma." (One can go to the cinema.)
* "We can" (ability): "On peut faire ça." (We can do that.)
* "It's possible": "On peut le faire." (It's possible to do it.)
Remember that "on" in French is often a vague, impersonal subject, similar to the English "one" or "you" in certain contexts.