The difference between the past simple and the past continuous

Main events and background events in a story

In a story which is told in the past tense, the main events (the ones that happen in the foreground and carry the story forward) are expressed with the past simple, while the past continuous is used for background events:

Ten people were sitting around the table. It was raining outside. Suddenly, the door opened and a woman entered the room. She was wearing a black dress. Everyone stared at, her but she didn't say anything. She slowly went to the table and put an envelope on it. They were just staring at her as she left the room.

Note the difference between these two sentences from the story:

Everyone stared at her.
They were just staring at her.

The past simple in the first sentence expresses a momentary, completed action, whereas the past continuous in the second sentence expresses an action in progress. Here is another example for the same contrast:

I went home at 7. (completed action)
At 7, I was going home. (action in progress)