French Imperfect Tense
L'imparfait is the imperfect tense of the indicative mood. It expresses actions which were happening, repeated, or habits in the past. The imparfait is (more or less) equivalent to the English past continuous, though sometimes it's better translated by the simple past.
To emphasize an ongoing action in the past, you can use the expression être en train de + infinitive.
See also: French Passé and All French tenses