Nirvana literally means "blown out". The flame of suffering, the flame of likes and dislikes and delusion has been blown out. One is not shaken from the always changing world anymore. One lives
in the Blessed State and experiences the everlasting and stable Reality behind this apparent world.
(Nirvana does not mean "nowhere", "nothing" or "nothingness" but the dissolution of the universe for whom the experience of nirvana takes place.)
Swami Yogeshwarananda told me :
The purpose of life is to know oneself and in order to know oneself man is brought into existence. Until he knows himself he keeps on living in this world taking birth after birth, life after life, and this process continues until this knowledge as to who he is and what he is, dawns in himself.
The day he realises who he is and what he is, that very day the lamp of his empirical existence is blown out. That is to say he attains the state of Nirvana which is otherwise termed as Moksha or Liberation, Redemption.
It is acknowledged (and said by Buddha) that there is something left over when we say "Nirvana". The concept or the meaning is "blown off"; the flame of the universe is blown out; the flame of our apparent existence is blown out. Immediately, then and there, the experience of the underlying Reality transpires. This is the implication of the word Nirvana. It does not mean absolute nothingness thereafter.
The external object is only a medium to give the state of happiness. If you can be free of this, your existence would be unconditional, irrespective of the presence or the absence of an object – this is called freedom. Irrespective of the presence of the object you will be unconditionally at ease with yourself, and that Supreme State wherein all desires disappear is said to be the state of Nirvana, no more than that.
OM tat sat