Past progressive, il passato progressivo
Uses: The past progressive is typically used to indicate that an action was in the process of happening (often used to juxtapose that action with another action that subsequently happened).
Its uses are very similar to the imperfect. E.g.,
Stava leggendo quando ha sentito un rumore strano.
She was reading when she heard a strange noise.
Stavano mangiando. = They were eating.
Similar to the note above about the present progressive, the main advantage of using the past progressive (as opposed to the imperfect) is that it can underline/emphasize that an activity was happening or developing at a past time.
Forms: The past progressive is formed with the appropriate imperfect form of stare and the gerund of the verb.
stavo
stavi
stava + -ando, -endo
stavamo
stavate
stavano
The same note about reflexive verbs made above (the reflexive pronoun can be placed before stare, or attached to the gerund), applies to reflexive verbs in il passato progressivo.
For example,
Mi stavo preparando/ stavo preparandomi, quando ha telefonato Marco.
I was getting ready when Marco called.
Si stava alzando/stava alzandosi quando ha sentito le notizie.
She was getting up when she heard the news.