What exactly are iStripper "Quest Points" ?

These are points earned in the current event, Event Quests.

Go to this (the tab immediately to the right of 'Featured', though it may have a different name until you click on it).
Back 2 School Event Quests.
Click the quests button.

Here is what mine shows:
Show quests, 0/5 completed
Slot Machine quests, 0/6 completed
Thrill Spin quests, 0/6 completed
Golden Ticket quests, 0/5 completed
Dolz quests, 2/8 completed
Bonus quests, 1/5 completed

As you complete these quests, you gain points.
1000 points let you attain the SEC card of Erin Pink.
I am not sure if the EX card of Atlantis Deep can be attained this way. I believe yes.

As you complete these quests, you gain points.1000 points let you attain the SEC card of Erin Pink.I am not sure if the EX card of Atlantis Deep can be attained this way. I believe yes.

I believe the screen shows that 1000 points and you get the Erin Pink card and 2000 points will get you the Atlantis Deep card.

@willyweekly,
Yes you are right.
1000 points for the Erin Pink card.
2000 points for the Atlantis Deep card.
Only one card shows at a time (for me, using 12376). But there is an arrow to click.
I believe that the points are 1000 for Erin Pink, and an additional 1000 for Atlantis Deep, totally 2000.