Nirvana is Sanskrit and means to be extinguished or to blow out (as in blowing out a candle). It’s often interpreted to mean blowing out the flame of illusion, or the self. In Pali nirvana is spelt nibbana. Hinduism and Jainism also talk of nirvana as the state of moksha.
Nirvana means freedom from suffering. When we recognise our true nature as Buddha nature, we enter nirvana. To blow out the self or the ego means the extinction of all concepts and ideas. The only way to realise ultimate reality and touch the ground of all being is to free yourself from all ideas about what reality may or may not be.
Of course, those ideas and concepts also include ideas about nirvana and Buddha nature. The Buddha talked about using Buddhism, or the Dharma, as a raft to cross the river. Once you are safely on the other side, you no longer need the raft. It is just a tool which helps you to liberate yourself from suffering. When you see your true nature and recognise nirvana as the ground of existence, you no longer need the Dharma.
Nirvana is not a separate place, like a kind of heaven that you waft off to when you become enlightened. As it is the ground of all being, nothing can be said to be separate from it. Indeed, nirvana is samsara, and samsara is nirvana.
“Nirvana means extinction, above all the extinction of ideas – the ideas of birth and death, existence and nonexistence, coming and going, self and other, one and many. All these ideas cause us to suffer… Nirvana is a fan that helps us extinguish the fire of all our ideas, including ideas of permanence and self.” – Thich Nhat Hanh, The Heart of the Buddha’s Teaching