た vs ていた

  1. Not present to observe action
    た is used to describe a fact that action occurred
    ていた is not used
  2. Present to observe action
    た is used to describe action occurred same time or immediately
    ていた is used to describe action already occurred
  3. Sequence of action
    た is used to describe actions that occurs in sequence
    ていた is used when another action occurs at the same time