Grammar: Past progressive vs Simple past

Past progressive

• actions in progress at a started time in the past.
  He was driving to work at 9 o'clock yesterday afternoon.
• actions that were happening simultaneosuly in the past.
  Bob was walking while Ben was running to catch the bus.
• past action in progress interrupted by another action. The action that interrupted the action in progress is the simple past.
  Jenny was having a shower when the phone rang.

Simple past

• action that happened at a started time in the past.
  He left yesterday afternoon.
• past actions that happened one after the other.
  She oppened the door, went into the office and walked toward the desk.