I've always thought of intelligence as the ability to learn, which you could say is the maximum speed you can gain knowledge and understanding. A person may be able to learn in some areas very well, but not so well in others. Also, someone who has devoted much time to gaining knowledge and understanding may be much less intelligent as someone who could learn quickly but never puts their mind to it.

An analogy for this view of intelligence and knowledge is like a car's acceleration and speed. Some cars may be able to go very fast but they may take a while to accelerate.

As others have mentioned in this thread, what obviously matters more is how you apply intelligence, knowledge and understanding.