In short: Prayer is the service, the submission of man's heart to G-d. It is the consciousness in man of the Omnipresent. It is the ladder on which man's soul ascends to become united with, and absorbed in, the Infinite.
Translated into practical terms, this means that prayer elevates man and matter.
This is indicated already in the statement that he who prays "should direct his eyes downwards and his heart upwards": 'downwards' -to the soul, the Divine Presence inherent to everything; 'upwards' - to the Holy One, blessed be He.
Through prayer we realize G-d's all-permeating presence, even in what appears to us as nature and matter. Through prayer we come to realize that G-d the Infinite (Divine Transcendence) and G-d manifest in the order and workings of the universe (Divine Immanence) is One, and there is nothing beside Him.
The soul, spirituality, Divinity, comes to the fore, penetrates matter, lends it its ultimate form, and confers upon it meaning and purpose. For when all of man's appetitive powers, all his interests and desires, are directed fully and consciously to the sublime (the concept of kavanah), then man himself, wholly and totally, soul and body, spirit and matter, is in that sublimity.
This process of self-elevation through prayer can actually be traced.
Though sometimes prompted by personal desire, self-centered wishes, the immediate cause of prayer is always reason. When the impulse of desire awakens, man's rational faculty seeks a way to realize that particular desire. As it considers the issue, it concludes that realization is possible only through Omnipotent G-d. Thus it is led to the decision that the appropriate thing to do is to pray to Him.
In carrying this decision to its logical conclusion, we set into motion a chain-reaction of reflection on one's personal status and subsequent self-improvement.
After all, the petitioner understands that he will have to put himself into the good graces of the Supplier. Begging a favor, he will seek to be pleasing and acceptable to Him on whom he is dependent for the fulfillment of his wishes.
Reflecting on the nature of G-d, in order to know the most effective method for successful prayer, he must realize that there are certain modes of behavior which are incompatible with his aims.
For example, of disobedience it is written - "He that turns away his ear from hearing Torah, even his prayer is an abomination" (Proverbs 28:9); of injustice - "Who also eat the flesh of My people and flay their skin from off them .. then they shall cry unto G-d but He will not answer them" (Michah 3:3); and likewise with other forms of misbehavior condemned by G-d.
To think of G-d, and to accept the idea of His Being (inherent in the very concept of prayer), of itself also implies the acceptance of His decrees.
It is altogether absurd to disregard G-d's wishes while asking Him to fulfill our own. Thus it is said, "As He called and they would not hear, so they shall call and I will not hear" (Zechariah 7:13).
It is equally absurd to expect the grace of a grant when refusing to be gracious ourselves: "Who so stops his ears against the cry of the poor, he also shall cry but shall not be answered" (Proverbs 21:13).
Tefilah, as indicated by another meaning of this term itself, thus is a trial, a form of judgment. In our context it is a form of self- judgment, to sustain and enhance that which is right and just already, to correct that which needs improvement, and to implement that which as yet is missing.
