Theory:

Simple past tense:
The simple past tense is used to refer to actions that were completed in a time period before the present time. The action may have been in the recent past or a long time ago.
Example:
1. I bought a new dress last week.
2. I lived in Chennai 8 years ago.
3. We just finished our lunch.
Simple past tense can be used for
  • completed events - Mani ran to class because he was late.
  • events in stories - The thirsty crow drank the water and flew away.
past tense_revised.jpg.svg
Mani ran to class because he was late!
Past progressive tense:
The past continuous/progressive tense refers to a continuing action or state that was happening at some point in past. It is formed by combining the past tense of to be (i.e., was/were) with the verb’s present participle (-ing word).
Example:
1. Mani was running to class because he was late.
2. The sun was shining every day that summer.
3. The children were laughing at my jokes.
Past progressive_revised.svg
Mani was running to class because he was late.
 
Uses of past progressive tense:
 
1. It can also be used to describe something that was happening continuously in the past when another action interrupted it.
Example:
i. The audience were applauding until he went off the stage.
ii. My father was making dinner when my mother arrived.
2. The past continuous can shed light on recalling what happened at a particular time in the past.
Example:
i. At 10 o’clock, I was eating dinner.
ii. Yesterday morning, I was reading newspaper when I got your call. 
3. It can also refer to a habitual action in the past.
Example:
i. Preethi was talking constantly in class in those days.
ii. We were buying from Rose Supermarket when we lived in Adyar.
4. To emphasize length or duration.
Example:
i. Pavitra was coughing all day because she was sick.
ii. I was practising Math all week because of my low scores.
Important!
Not every verb is suited to describing a continuous action. Certain verbs can’t be used in the past continuous tense.
 
Example:
 
i. At noon, Rehman was arriving. (Wrong sentence) , arrived(correct).
ii. Yesterday morning her grandfather was dying. (Wrong sentence), died (correct).