Could you explain the imperfect tense?

The imperfect tense conveys an action that happened in the past. However, this differs from the perfect tense as imperfect implies the action was continuous / happened regularly in the past. It can be compared to English when we say 'I used to play' or 'I was playing'. In order to form the imperfect tense you: (1) take the nous form present tense verb e.g. nous faisons (2) drop the 'ons' on the end of the verb to get the stem -> fais (3) add the imperfect ending that corresponds to the subject pronoun [je - (fais)ais; tu - (fais)ais; il/elle/on - (fais)ait; nous - (fais)ions; vous - (fais)iez; ils/elles - (fais)aient
]. Most verbs follow this pattern, however there are some verbs that do not. e.g. for the verb être the stem would be 'ét' (J'étais, tu était, il/elle/on était, nous étions, vous étiez, ils/elles étaient)