Past forms include the past simple, past continuous, past perfect, and past perfect continuous. The past continuous uses "was/were + verb-ing" to describe actions that were ongoing or in progress at a specific time in the past. It is used to talk about background scenes, actions interrupted by other events where the longer action is in the past continuous and shorter in the past simple, and simultaneous past actions. Key uses are to describe actions happening at a stated past time, interrupted or background actions, and multiple simultaneous past actions.