You have probably heard of the Part of Fortune, but there are actually quite a few Arabian parts in the horoscope. They are points that are calculated by adding 2 planets together and subtracting another planet from the equation.
For example, the Part of Fortune is arrived at by adding the Ascendant to the Moon, and subtracting the Sun.The reasoning is that the ascendant represents you in the outer world, combined with the moon, your innate qualities. When you subtract the sun(which represents your potential to grow), you are left with what will come to you naturally.
On the other hand, the Part of Spirit is The Ascendant plus the Sun, minus the Moon.
When you add the ascendant and sun and subtract the moon you see your potential to grow in the outer world in things that will probably require more effort because they are not inborn to you and you have to go out and get them.
As I said, there are many Arabian parts. Here are a few:
Part of Love
Part of Fortune
Part of Spirit
Part of Marriage
Part of Children
Part of Fame
Part of Friends
Part of Accomplishment
The list goes on. In the old days these points had to be calculated by hand, which wasn't very hard, but still a bit tedious. I found a website with a calculator so you can easily find them. I apologize I'm not expeienced enough to get a link so I will give the address.