The Past Continuous tense can be used for several purposes It is initially applied in the description of an activity which was in progress at a particular time in the past.
Secondly, it can be used in the situation of one action interrupting the other. In this type of situation, the longer action requires the use of the past continuous tense, whereas the other action requires the simple past tense.
Also, it demonstrates two actions taking place at the same time in the past. They were studying while their parents were cooking.
subject + was/were + ing
I was taking shower when you call he
I was walking to school when I met my friend