It can be confusing to know when to use the simple past and when to use the past continuous. In general, we use the simple past and the past continuous differently like this:
Completed Events in the Past
If you are talking about something that happened in the past and is completed, use the simple past. This action can last a short amount of time or a long amount of time. It can be about something that happened recently or something that happened a long time ago. You can also use the simple past to talk about something that happened once, or something that happened many times.
The most important thing is that the simple past is used to talk about something that is completed. Here are some examples of simple past sentences.
The food in my kitchen only lasted for five minutes!
The food in my kitchen lasted for five years!
My grandparents danced together last night.
My grandparents danced together sixty years ago.
Henry brought a new dog home one day.
Henry brought a new dog home every day!
In-Progress Events in the Past
If you are talking about something that happened in the past and is happening at the exact moment in the past that you are writing about, use the past continuous. You can also use the past continuous to talk about events or activities that happened over an extended period of time. All these events can still be going on, or may have stopped and started again.
The most important thing is that the past continuous is used to talk about a past event that was happening at the moment, or lasted a long time. Here are some examples of past continuous sentences.
She was making a very, very big bubble.
Martin was building his house of cards for two years!
Background Information
Sometimes, we also use the past continuous to give background information, especially when telling a story. You will often find that books use the past continuous to set a scene. Here are some examples.
It was snowing outside.
The birds were singing loudly in the tree.