Can someone break down for me the difference between compound past tenses and subjunctive tenses in French?

I'm in French 3 and my teacher really stinks at breaking down the "how's" and "when's" of using the plus-que-parfait tense from the imparfait, to the subjontif, and I have no idea how or when to use them. We have an oral exam this Monday on a surprise topic we won't receive until Sunday evening and we'll have to discuss with her what we know about it, while she'll yze our ability to pose statements in the various verb tenses. We were introduced these very fast with no thorough coverage of their operation and I need help. Merci d'avance pour vous qui peut m'aider..