Listed below are uses with examples, and the structure of the past continuous tense.
Something happening at a specific point of time in the past
I was watching TV at 9 o'clock last night.
They were working on the report at six.
Something that was happening during a period of time in the past
We were studying during the recess.
Peter was sleeping during class.
Something that was happening when something important took place
She was speaking on the phone when he arrived.
When he won the game, I was cooking.
Something that was happening while something else was happening
She was working on her homework while I was preparing dinner.
They were finishing the project while we were putting together the proposal.
Common time expressions used with the past continuous:
at six, nine o'clock, etc. during, while, when
Subject + conjugate the helping verb "be" + verb + -ing.
I was, You were, He was, She was, We were, You were, They were - watching TV when I arrived.
Subject + conjugate the helping verb "be" + not + verb + -ing.
I wasn't, You weren't, He wasn't, She wasn't, We weren't, You weren't, They weren't - working when he came into the room.
Question word + conjugate the helping verb 'be' + subject + verb + -ing
What - were you, they - doing at seven o'clock?
What - was I, he, she - doing at seven o'clock?