Past progressive tense describes a past action which was happening when another action occurred. This tense is formed by using was/were with the verb form ending in -ing.
The PAST PERFECT TENSE indicates that an action was completed (finished or "perfected") at some point in the past before something else happened. This tense is formed with the past tense form of "to have" (HAD) plus the past participle of the verb (which can be either regular or irregular in form):
