Subject + was/were + gerund + object
The past continuous has no unique conjugations. It uses the past of to be plus the gerund and follows the spelling rules for gerund structures.
We use the Past Continuous to:
talk about something happening at a particular moment in the past
I was walking to school yesterday
We were planning our holiday in March
A Past Continuous action is often used in combination with another action, as the Past Continuous is used to express the background action, what was happening when something else happened. This is often called the long action.
Action A) I was walking to school
Action B) I saw the accident
Action A the "long action or "background action" is interrupted or unfinished when the "short action", or specific moment in the past occurs.
Narrative tenses: The Past Continuous is often referred to as a narrative tense, these are the past structures we use to tell stories.
Differences between Past Simple and Past Continuous here
Further Functions for the Past Continuous can be found here