difference between imparfait and passé composé and when is it the right time to use them?

The imperfect is used for description, talk about a habit. The action is incomplete:Exemple : When it was cold he did not forget to put his gloves on the mantelpiece.(Quand il faisait froid  il n'oubliait pas de mettre ses gants sur la cheminée.)Here it is a habit. For the past tense; action is accurate and complete.  Exemple : He put his gloves on fire home from work.(Il a mis ses gants sur la cheminée en rentrant du travail.)He did it once, it happened dated.