I had been waiting for you
I waited for you
we had been sleeping
what is main difference between these sentences? And when to use Simple Past and when to use Past Perfect Continuous?
We use different past tenses to describe moments and periods of time in the past.
When Andrea arrived at work at
----------8.30 am----------9.00 am----------
9.30 am----------10.00 am----------
1) When Andrea arrived at work at 9.30, she could see the post over her desk. Her secretary had opened it before she came. (The secretary opened the post between 8.00 am am and 9.00 am, in a distant past)
2) When Andrea arrived at work at 9.30, her secretary was opening the post. (The action is happening at 9.30)
3) When Andrea arrived at work at 9.30, her secretary opened the post. (The action finished between 8.00 am and 9.25 am)
Your question isn't silly at all.
The Past Simple tells a story in chronological order...
Sue met Pete at university. They were together for six years. They divorced last month.
... while Past Perfect can be used to tell a story in a different order.
Sue and Pete divorced last month. They had met at university, and had been together for six years.