The imperfect past tense is used when:-speaking of an event in the past that has happened repeatedly (eg: tous les jours j'allais à l'école)-describing a person, object or event in the past (eg: il avait un manteau noir)The simple past tense is used when referring to something that happened at a specific time, it is focused on the action itself rather than the description of what is happening (eg: il mit ses chaussures)