Balls: Curve or Straight?

Before your mind beings to wander, I'd like to state that the content of this post is quite innocuous.

I went bowling with a few friends yesterday and I discovered an interesting new fact.

Let me give you some background info: See, the thing is.. I've been bowling in Bahrain since I was 15. That's 7 years. I had a phase between 15 and 16 where I used to bowl every other day at Bushihri (old school bowling place which I believe has been unfortunately shut down recently). Obviously I'm out of shape these days since for the last 5 years I've been abroad and haven't bowled much on the occasions that I did come back. I would say I'm a decent player, averaging 135 per round on a good day.

Okay, so I've got some experience when it comes down to it, right? I even know how to calculate spare and strike scores! How come I've never heard about the curve and straight variations of the ball until yesterday?

Apparently, the curve ball is the one the professionals play with. You roll it down the lane and it looks like its going to take out 2 or 3 pins max, but then it takes a wicked curve and heads towards the middle, resulting in a strike most of the time. I've known that the method existed, but I never knew it had its own seperate ball. The balls provided for the masses placed on the racks are all straight balls, and I've been using those for the last 7 years.

No wonder all my finger-breaking attempts at generating that curve from a straight ball have proved so painfully unsuccessful.