Difference between On-the-job and Activity

On-the-job

Part of speech: adjective

Definition: obtained whilst working

Activity

Part of speech: noun

Definition: The state or quality of being active; nimbleness; agility; vigorous action or operation; energy; active force; as, an increasing variety of human activities.something done as an action or a movementsomething done for pleasure or entertainment, especially one involving movement or an excursion.Use (of internet, playstation, bank account etc.)

Example sentence: Philosophy is not a theory but an activity.