Past continuous (I was doing) в английском языке

Study this example situation:

Yesterday Dave and Jim played tennis. They began at 10:00 and finished at 11:00. What were they doing at 10:30? They were playing tennis (at 10:30). "They were playing" means that they were in the middle of playing tennis. They had started playing, but they hadn't finished. This is the past continuous tense: I/he/she was we/they/you were } playing

We use the past continuous to say that someone was in the middle of doing something at a certain time. The action or situation had already started before thus time but hadn't finished:

• This time last year I was living in Brazil.


• What were you doing at 10:00 last night?

The past continuous does not tell us whether an action was finished or not. Perhaps it was finished, perhaps not. Compare:

• Dan was cooking dinner, (past continuous) = He was in the middle of cooking dinner and we don't know whether he finished cooking it.


• Dan cooked dinner, (simple past) = He began and finished it.

We often use the past continuous (I was doing) and the simple past (I did) together to say that something happened in the middle of something else:

• Dan burned his hand while he was cooking dinner.


• I saw Jim in the park. He was sitting on the grass and reading a book.


• It was raining when I got up.


• While I was working in the garden, I hurt my back.

But to say that one thing happened after another, use the simple past.

• Last night Sue was taking a bath when the phone rang. She got out of the bathtub and answered the phone.

Compare:

• When Helen arrived, we were having dinner, (past continuous) = We had already started dinner before Helen arrived.
  
• When Helen arrived, we had dinner, (simple past) = Helen arrived and then we had dinner.
  

Note: There are some verbs (for example, know) that are not normally used in continuous tenses. For a list of these verbs see this.