Past continuous is used when an action was in progress in past and usually is used with another action and doesn’t come by itself.
Verb to be (was, were) + ing
She was driving when I saw her passing by.
To make the tense clearer read the following story.
“Sara and Sabina are twins from India. When they graduated from high school their parents decided to send them to the US to continue their studies. They became very happy to hear that from one side but from the other side they knew they were going to miss their family.
At first, they chose the state and university that they were going to attend and then after a few months they were ready to leave their country.
As they were packing their luggage on the night of their flight their parents gave them a long speech to how to live there on their own.
As they were listening tears kept coming down of their eyes because that was the first time they were away from their home and country.
Finally, they were at the airport and as they were waving goodbye to their parents they headed for a new and unknown future.
They still were in shock of the new place when they got there but after some time they got used to the new situation and their classes started and kept them busy.
They are still there and busy with their classes but now if you talk to them they give you memories that were strange and funny.
Sometimes when life is all hard and strange for the time being may look funny and without any worries some years later.”
As you can see from the story above the whole event is about past tense but when two actions happened and one was in progress past continuous was used.
“…they knew they were going to miss their family…”
“….as they were packing…”
Hope these explanations and the story can come handy to you.