When would you use perfect tense and when would you use the pluperfect?

The perfect tense is used when in English you would say something has/ hasn't happened: for example, 'she has read the book', 'he hasn't finished it yet.' The pluperfect is used when in English you would say something had/ hadn't happened: for example 'I had eaten the apple', 'she hadn't seen the car.' When using the pluperfect you are often implying that this particular action happened before something else, it is slightly further into the past than the perfect and the preterite: for example 'he hadn't finished his homework before his friend rang.'