IQ is like the central processor of a computer. Computer speed is dependent upon it. So IQ in essence measures how quickly a person learns and functions, but not necessarily how deeply one learns. That is more in the hands of intellect, the ability to see the big picture and connect the dots. IQ and intellect often go hand in hand but not always.
Sometimes a deficiency in IQ is compensated by a more powerful intellect. The absentminded professor type comes to mind as one example of depth over speed. But in most practical matters of day to day function and advancement IQ is the greater advantage,