Past Simple VS Past Continious

Past simple: we use the Past Continuous to indicate that a longer action in the past was interrupted. The interruption is usually a shorter action in the Simple Past. Remember this can be a real interruption or just an interruption in time.
examples: I was watching TV when she called.
When the phone rang, she was writing a letter.
While we were having the picnic, it started to rain.
What were you doing when the earthquake started?

Past continuousd: we use the Simple Past to express the idea that an action started and finished at a specific time in the past. Sometimes, the speaker may not actually mention the specific time, but they do have one specific time in mind.