The passé composé (compound past tense) is used to refer to an action or event that began and was completed at a particular moment of time in the past. Two elements are required to form the passé composé: a helping verb (either avoir or être) and a past participle (usually the ‐ed form of an English verb).
Introduction to Past Tenses
The passé simple is a literary past tense, most often used in writing, and also refers to an action or event that was completed in the past. The passé anterieur, which is very limited in use, is the compound form of the passé simple. (The passé simple of the correct helping verb is followed by the past participle of the verb indicating the action.)
The imperfect (l'imparfait) is a simple tense used to refer to an ongoing or habitual action in the past and describes incomplete actions, situations, or events in the past. The plus‐que‐parfait is the compound form of the imperfect (the imperfect of the correct helping verb is followed by the past participle of the verb indicating the action) and indicates what had been going on in the past.