The G-dliness of the tzaddik gives him a deeper spiritual perception and understanding of an individual, the world, and the heavenly plane. When he sees a need — that a person is not well, has no children, money, or any other problem, G-d forbid — the tzaddik is able to perceive the source of the problem on a spiritual level: he can see the person’s spiritual deficiency causing this physical lack, or is privy to the decree in heaven that brought it about.
When a tzaddik prays for someone, he is not just requesting that the symptoms of a person’s problems either disappear or change in the physical realm. Rather, he is reaching into the spiritual realms in search of the inner core of the problem and praying for healing at that level. Once the core of the issue is corrected in the spiritual realm, the symptoms will naturally fall away in the physical realm.
When the average person davens, his or her words may reach the spiritual worlds, but he himself cannot see into the spiritual realms at all. In general, all he can basically perceive is the physical end product of whatever is transpiring above. But because a tzaddik has a clear window into the spiritual world, he is able to direct his prayers to the proper channel in a much more precise and powerful way.
As an example, if a person has a broken machine, he tries to figure out why it is not working. He pushes this or that button, turns the machine on and off, checks the wires, etc., and if he still can’t get it to work, he brings it to a technician. The technician opens up the machine and looks inside for the source of the problem. The layman can only deal with whatever is on the surface. His knowledge extends only to the knobs, buttons and wires that are on the outside of the machine. The technician looks at the inner workings of the machine, gets to the root of the problem, and fixes it on a more fundamental level.
