was/were + gerund (verb + ing)
We use the past continuous to talk about an action in the past that was prolonging or that was about to be interrupted.
I was studying yesterday for over five hours.
You were watching the game yesterday when your mum came in. ( ‘your mum came in’ is interrupting the action of ‘watching the game’).
What were you doing on Saturday? I was playing video games.
We use the past continuous to talk about parallel actions in the past (more than one action occurring at the same time).
They were working yesterday while their colleagues were enjoying their time outside.
She was helping her friend while her friend was cleaning her room.
We can use the past continuous to talk about the atmosphere or ambiance of the past.
When we entered the mall there were people yelling and shoppers were screaming at one another.
Yesterday when I went to the football game I saw that people were happily cheering on their local teams.
What were you doing in the office after hours yesterday? I was just hanging around to see if could find my friend.
She was never going to see him in the first place.
When she arrived yesterday I was still waiting for her for over thirty minutes.