Realization of nirvana (Pali: nibbana; Chinese: 涅槃) is not containable by words. But there is a necessity to speak in order to attempt to communicate this human potentiality and encourage people to realize nirvana.
Pictorially, the moment of realising nirvana is like a sudden, even instantaneous, eruption of penetrative energy beyond all that is known, knowable, and knowing. It is like an immensity of thunderbolt traversing earth to heaven, not by its own strength but by a magnetic pull beyond conception. Blissful beyond measure, ecstatic and vibrant, its destination point is a timeless and spaceless cessation of all that is, was, and ever will be. Everything stops.
It is as if the vast expanse of sky crackles with infinite vibration and utterly shatters into oblivion, with that escalating touch of ecstatic insight reaching from earth to heaven. Blissful, luminous, imageless knowing that intensifies and expands throughout the process, it all finally meets its end in total stopping. All that is born of delusion gets burnt up in the white fire of the thunderbolt as it warp-speeds and hyper-spaces into the beyond.
Returning from the source, one is forever transformed and liberated from eons of psychic accumulation. The delusion of self is forever eliminated. One can never hold onto the wrong view of self (sakkaya-ditthi) ever again. The illusory drama and magic show of material and intellectual existence loses its hold over one. Even mystical experiences are seen in their right place and perspective.
The task from then on is to immerse again and again into that utter freedom of the mind (anuttara-ceto-vimutti) where all stands still. Process is gradual. Breakthrough is sudden. Each occasion of nirvanic breakthrough removes ever subtler accumulation of delusion till not even a trace of self-grasping remains.
Buddhahood dawns. From moment to moment, in everyday life, one can enter into this freedom of timeless stopping by mindful recapitulation of the nirvanic process. This need not be full blown but trailing waves of unconditioned bliss can pour forth from timelessness into time, spacelessness into space, selflessness into self (relative and imputed). No more striving or self-occupied control. Just dynamic impulses of intent without anyone intending.