Some excerpts from the teachings of Prabhupada.
Kṛṣṇa, being absolute, is not different from His words. The words of Kṛṣṇa and Kṛṣṇa Himself—they are the same. That is the meaning of Absolute Truth.
In the relative world, the word water and the substance water are different. When I am thirsty, if I simply chant "Water, water, water," my thirst will not be satisfied. I require the real water. That is the nature of the relative world and relative consciousness. But in the spiritual world or spiritual consciousness, the name is the same as the thing that is named. For instance, we are chanting Hare Kṛṣṇa. If Kṛṣṇa were different from the chanting of Hare Kṛṣṇa, then how could we be satisfied chanting the whole day and night? This is the proof. An ordinary name—if you chant "Mr. John, Mr. John," after chanting three times you'll cease. But this Hare Kṛṣṇa mahā-mantra—if you go on chanting twenty-four hours a day, you'll never become tired. This is the spiritual nature of the Absolute Truth. This is practical. Anyone can perceive it.
The method is vibration of transcendental sound. This Hare Kṛṣṇa, this sound, is not material sound. It is descended from the spiritual world. Kṛṣṇa and Kṛṣṇa's name—not different. Abhinnatvāṁ nāma-nāminoḥ. As in this material world there is difference between the name and the substance... If you are thirsty, then if you simply chant "water, water, water," your thirst will not be quenched. You have to get the substance water. But in the spiritual world it is, being absolute, the name and the person whose name we are chanting, they are the same. Therefore by chanting this holy name of God, Kṛṣṇa, Hare Kṛṣṇa... Hare is addressing the spiritual energy of the Lord, and Kṛṣṇa is the Supreme Lord. So by being in touch with the Supreme Lord and His energy directly, we become purified. Exactly like if you take one iron rod, put into the fire, it becomes warner, warmer, and at last it becomes red hot. When it is red hot, it is no longer iron; it is fire. Similarly, if you constantly become in touch with the Supreme Lord by chanting His holy name, which is not different from the Supreme Lord, then you become spiritually purified. And as soon as you are spiritually purified, then all misunderstandings of this material world immediately vanquished. That is called Kṛṣṇa consciousness.
I have already explained that God and His name, the one, Absolute. In the material world your name and you, person, they are two different things. That is difference between God and you. So therefore, by chanting God's name, you actually contact with God. But in the material world that is not possible. Suppose I am thirsty; I want water. If I chant "water, water," it will not act. But in the case of chanting the holy name of God, it is as good as to associate with God.
nāma cintāmaṇiḥ kṛṣṇaś
caitanya-rasa-vigrahaḥ
pūrṇaḥ śuddhaḥ nitya-mukta
abhinnatvāt nāma-nāminoḥ
“‘The holy name of Kṛṣṇa is transcendentally blissful. It bestows all spiritual benedictions, for it is Kṛṣṇa Himself, the reservoir of all pleasure. Kṛṣṇa’s name is complete, and it is the form of all transcendental mellows. It is not a material name under any condition, and it is no less powerful than Kṛṣṇa Himself. Since Kṛṣṇa’s name is not contaminated by the material qualities, there is no question of its being involved with māyā. Kṛṣṇa’s name is always liberated and spiritual; it is never conditioned by the laws of material nature. This is because the name of Kṛṣṇa and Kṛṣṇa Himself are identical.’
PURPORT
This is a quotation from the Padma Purāṇa.
http://vedabase.net/cc/madhya/17/133/