While the passé composé is used to refer to specific past events of interest, the imparfait can loosely be thought of as describing “background information” such as:
- States of being and habitual actions:
“Quand j’était petit, je jouais le piano.”
- Actions of an unspecified duration. Descriptions of time, weather and feelings:
“Il faisait beau. Tout les oiseaux chantaient. Elle était très belle. Il l'aimait.”
- Actions that are in progress when a sudden event occurs:
“Je dormais quand le téléphone a sonné.”