1. The most common use of the past continuous tense is to talk about something that was happening around a particular time in the past.
What were you doing at 8 o’clock last night? I was watching television.
I started watching television before 8 o’clock and I continued watching it after 8 o’clock.
In 1994 he was working in a small town in Poland.
At 6 o’clock on Saturday morning we were travelling to the airport.
2. We often use the past continuous and the past simple tense together. When this happens, the past continuous describes a longer, ‘background’ action or situation and the past simple describes the action or events.
When I woke up this morning it was raining and my father was singing in the kitchen.
I was walking home, whistling happily, when I saw two masked men run out of the bank.
Often, the ‘action’ described by the past simple tense interrupts the ‘situation’ described by the past continuous tense.
I broke my leg when I was skiing.
I was playing a computer game when the doorbell rang.
Notice that the past continuous describes ‘situations’ that go on for some time – ‘skiing’ and ‘playing’ but the past simple describes ‘actions’ that happen quickly – ‘broke’ and ‘rang’.
Notice too the important difference between these two sentences.
When they arrived, Jeff was cooking dinner. Jeff started cooking before they arrived.
When they arrived, Jeff cooked dinner. Jeff started cooking dinner after they arrived.