The speaker is reflecting on actions that occurred before other events in the past. These actions are presented in different forms:

• Affirmative (Positive): Subject + had + verb (past participle)
  Example: We had won 3 gold medals by 1pm on the first day.
• Negative: Subject + had + not + verb (past participle)
  Example: I had not eaten fish and chips until I came to the UK.
• Question (Interrogative): Had + subject + verb (past participle)?
  Example: Had you ever played baseball before you moved to the USA?