Past Simple and Past Continuous refer to completed actions in the past.
Past Simple: We use it most of the time when we are talking about such actions.
We use it for something who occured. Here, the action is finished.
It’s the most common way of talking about the past.
I lived in London for 6 years.
He asked me but I didn’t know anything.
Peter phoned me yesterday at 8.00 pm (the conversation is finished now!)
I lived in Cambridge for my studies. (it was only for my studies!).
Past Continuous: We use it when we want to emphasize the continuity of the action.
We use the Past Continuous for an action in the past. Here, the action isn’t finished.
I was thinking about her the other day.
Everybody was talking about it all evening.
Past Simple + Past Continuous in the same sentence:
Past Continuous: it describes the action (I was doing…)
Past Simple: it describes that something happened during this action.
I was reading your mail when you rang.
I was doing my english exercise when Peter phoned me.
He was going out to lunch when she rang him.
He was reading a book, when Peter asked him something. (I haven’t finished to read my book!).
It was raining hard when we arrived.
TO KNOW and TO WANT: they are used only in a Past Simple form…
We don’t say:I’m knowing, I was knowing…NO!!
I’m wanting, I was wanting….NO!!
My girlfriend was reading a book, and I wanted to go to the cinema!