What is the past perfect verb tense? I never really understood the meaning of this. Please help!

Thanks

Past perfect always has the auxiliary verb "had" in it.

http://www.chompchomp.com/terms.htm
Click on Verbs.

https://www.google.com/search?q=past+perfect+tense+english&oq=past+perfect+tense+english&aqs=chrome..69i57.5396j0j7&sourceid=chrome&ie=UTF-8