Study this example situation:

Yesterday Sarah and Jane played tennis. They began at 9 o’clock and finished at 11. So, at 10 they were playing tennis.

Yesterday Sarah and Jane played tennis. They began at 9 o’clock and finished at 11. So, at 10 they were playing tennis. - English Grammar - Past Continuous (I was doing)
Yesterday Sarah and Jane played tennis. They began at 9 o’clock and finished at 11. So, at 10 they were playing tennis.

 

They were playing = “they were in the middle of playing”. They had not finished playing.

Was/were -ing is the past continuous:

Was/were -ing is the past continuous. - English Grammar - Past continuous (I was doing)

We use the past continuous to say that somebody was in the middle of doing something at a certain time. The action or situation had already started before this time but had not finished:

We use the past continuous to say that somebody was in the middle of doing something at a certain time. - English Grammar - Past continuous (I was doing)

  • This time last year I was living in Paris.
This time last year I was living in Paris. - English Grammar - Past continuous (I was doing)
This time last year I was living in Paris.

 

  • What were you doing at 10 o’clock the day before yesterday?
What were you doing at 10 o’clock the day before yesterday? - English Grammar - Past continuous (I was doing)
What were you doing at 10 o’clock the day before yesterday?

 

  • I waved to her but she wasn’t looking.
I waved to her but she wasn’t looking. - English Grammar - Past continuous (I was doing)
I waved to her but she wasn’t looking.