Tense

Perfect tenses simply mean the verb's action is complete. With present perfect the action is complete now; with past perfect the action was completed in the past.

Present perfect:
"I HAVE EATEN my dinner. Now can I have a cookie?"
"My daughter HAS TAKEN my car. We'll have to take yours."
"We don't need to buy a map; your father HAS DRAWN one for us."

Past perfect:
"We HAD GOTTEN up early, since the surf was best before dawn."
"I HAD FINISHED the test early, so I spent the rest of the period doodling."
"If she HAD WORN the black dress, no one would have noticed the stain."