A core tenet of Gaudiya Vaishnava philosophy is the doctrine of nama-tattva—the truth that the Supreme Lord is non-different from His holy name. In the material world, duality exists. The word "fire" cannot burn you, and the word "mango" cannot satisfy your hunger, because the designation and the object are entirely separate.
However, in the absolute spiritual realm, there is no duality. The shastras declare abhinnatvān nāma-nāminoḥ: the name of the Lord and the Lord Himself are identical. When we utter the word "Krishna," Krishna is personally manifesting before us in the form of sound vibration. The holy name contains all of Krishna's potencies, His forms, His qualities, and His pastimes fully intact.
For a neophyte practitioner, this truth may seem theoretical because the heart is covered by material illusions, preventing the direct perception of the Lord in His name. But as the chanting continues and the heart becomes purified, the devotee progressively realizes that the holy name is a living, breathing reality. Ultimately, for a pure devotee, chanting the name of Krishna is an experience of intense spiritual ecstasy, identical to seeing Him face-to-face.