What is the difference between the use of l'imparfait and le passé composé

Le passé composé is one of the past tenses. It is formed by using an auxiliary/first verb (either être or avoir) in the present tense and following it with the past participle of the desired verb. L’imparfait is also a past tense which is formed by combining the stem of the desired verb with the following endings·        Je: -ais·        Tu: -ais·        Il/elle/on: -ait·        Nous: -ions·        Vous: -iez·        Ils/elles: -aient
The best way to distinguish between the two types of past tense here is to consider their time scale. Le passé composé
A completed with a definitive end e.g. Last Friday I went to the cinema
L’imparfait Continuous or repetitive action e.g. I used to go swimming every week. Something over a longer period of time e.g. When I was younger, I studied Spanish.  These two tenses can also be combined to describe the interruption (le passé compose) of an action in the past (l’imparfait) e.g.
I was taking a shower when the telephone rang.
Je me douchais quand le téléphone a sonné.
Having a shower is an action in the past that is ongoing (l’imparfait) until it is interrupted by the one-off event of the phone ringing (le passé compose).