What is the difference between the imparfait and the passé composé in French?

I would first make sure that the student knows the difference between the tenses in English, for example , the difference between 'I was going to the shops' 'J'allais aux magasins' and 'I went to the shops' 'je suis allé aux magasins. I would emphasise that with the first statement, we have no indication as to whether the action has ended or not, whereas with the second statement, we can be sure it has ended.For this reason, a state of feeling eg' j'aimais l'école' can be used to describe an on-going feeling whereas with 'j'ai détesté l'école', we can be sure this is a previous feeling.The imparfait is also used to describe things which happen on a regular basis, for example 'je jouais au foot trois fois par semaine' I played football three times a week, whereas if you were describing one occurrence, you would say 'j'ai joué au foot hier soir' I played football yesterday evening.