Past progressive tense is used to indicate that an action was in progress when another action occurred in the past.

Past progressive (was/were + Ving) refers to the action in progress, and simple past tense refers to the “interrupting” action.

• While I was eating dinner, the telephone rang.
• The telephone rang while I was eating dinner.
• When the telephone rang, I was eating dinner.
• I was eating dinner when the telephone rang.

Past continuous can also be used to indicate only one action which occurred in the past:

• What was John doing yesterday?
• He was working at the factory.
• What were they doing yesterday afternoon?
• They were playing soccer.
• What were you doing last night?
• I was studying English.