In French, the imperfect is used to describe a scene (il FAISAIT beau), to say that you did something regularly in the past (je MANGEAIS un burger toutes les semaines) or to describe a continuous action in the past (je COURAIS très vite).
It is formed by taking the nous form of the present, taking off the 'ons' and adding the endings (ais, ais, ait, ions, iez, aient). For example, if I want to say "you (plural) used to say", I would take the nous form of the present (nous disons), take off the ending and add iez. "Vous disiez". Et voilà!